The film opens at Acme Looniversity on the last day of school, and the students are anxiously awaiting for the end of the day under the watching eyes of Bugs Bunny. The kids start singing a song about the long time they're waiting for the clock to hit three o'clock, and explain the things they intend to do this coming summer. Finally, after their song is done, Gogo breaks out of the clock to announce that school's out. The students rush out of the school and sing the movie's opening theme (sung to the tune of the show's theme song).
Later that day, Plucky is taking a walk with Hamton, inquiring him as to what he wants to do with him first, the choices being going to the beach, camping, or just watching TV. Hamton instead says that he's going out of town this summer, because he and his folks are going to the Happy World Land amusement park. Plucky, upon hearing this, wants to go to Happy World Land too and clings on to Hamton's leg, but Hamton detaches him and the Pig family leaves him behind. Plucky tries to get the Pig family to stop by disguising himself as a road constructionist and holds up some signs telling them to stop, but the Pigs don't notice him because they're videotaping their car hitting 100,000 miles and run over him in the process. (Then they drive over him two more times because Wade left the camera's lens cap on the first time.) Plucky then manages to get them to stop by making his own leg look like that of a pretty woman's. He pretends to say he'll be fine with not coming along on the trip, which moves Hamton enough to ask his parents if Plucky can come along. Wade agrees to letting Plucky come along, but the duck soon finds he's going to regret this when he finds he has to sit with Hamton's Uncle Stinky.
Meanwile Pac-Man, Ms. Pac-Man & Pac-Baby are almost out of gas. They head for Acme Acres to find a gas station. Behind them the Ghost Monsters along with their bratty 3 year old cousin Dinky (who wants an ice cream cone) are near by & they stop in Acme Acres. The Pacs find no gas station. They instead find Babs Bunny's rabbit hole. They soon meet up with the ghosts.
Then Babs come out of her hole and wile doing an impression of Robin Leach to herself, gets out everything she needs for sunbathing, including a backdrop of the French Riviera. She talks with the Pacs & the ghosts for a wile then they all take a nap. But while they sleep, Buster approaches them with his Acme Super Squirt gun. He brings down an Arctic backdrop and runs up to a refrigerator, where he pulls out a bucket of water and a tray of ice cubes (among other things). After mixing the ice into the water bucket and then filling it into his squirt gun, he returns to Babs and squirts her in the face. The alarmed Babs dashes into her burrow and hides in her mom's arms. When Buster comes up to her, Babs's mom scolds him for "squirting Babs inside the burrow" and throws them back outside, so Buster squirts her again. Babs furiously dashes back inside and gets out her own squirt gun, which she then demonstrates on the cameraman. However, she has no luck trying to squirt Buster herself. In the course of their chase, they pass by Elmyra's backyard, where Elmyra is trying to give Furball swimming lessons. Babs tries to steal Elmyra's wading pool to use against Buster, but Elmyra calls her out on it and demands it be given back (during which Furball considers cutting his tail off so he can escape), so Babs dumps the pool on Elmyra, allowing Furball to escape. Wile they have their fight as the Pacs & the ghosts wake up they try to find Buster & Babs to stop the water fighting nonsence. The ghosts all split up.
Inky who was looking everywere sees Babs heading to Acme Acres' dam and cranks it open, allowing the water contained to spill out all over the city. The Pacs & the ghosts try to stop her but its to late. Observing the flood she's causing, Babs decides to herself that "Perhaps I went too far, but Buster will get drenched for sure!" But Buster zips by on a jetski telling her, "I wouldn't say that!", drenches her with a wave from the impact of his jetski, and zips off to the Hawaiian islands. He tosses a barrel of dynamite into a volcano there, causing it to erupt and create a massive water wave that Buster, having now traded in his jetski for a surfboard, surfs on ("I do this water thing to them throughout the entire video"). After Babs the Pacs & the ghosts get caught in the flood created by this wave, Buster lands on a table floating near her and asks for her surrender, which she reluctantly agrees to. They also help up the Pacs & the ghosts who were not impressed. Babs climbs onto the table with them and finds that there's something stuck on her foot - Byron, Elmyra's basset hound. The current then takes their rafting table into a nearby river, taking the three of them out of Acme Acres.
Over at the beach, Shirley is running a fortune telling booth as her summer job and sees Buster and Babs, Pac-Man, his family & the Ghost Monsters escapade on her crystal ball. Fowlmouth comes up to her, asking if she wants to go see a movie with him, but she rejects his offer and tosses him to some volleyball players (such as Little Beeper, Sneezer & Sweetie). Fifi La Fume comes up to Shirley and tells her that she's looking to meet her idol, a movie star skunk named Johnny Pew, and wants him to autograph her photo of him. By looking at her aura, Shirley tells Fifi that Johnny is heading for the Acme Resort Hotel, so Fifi heads off there. Fowlmouth makes another attempt to ask Shirley to go to the movies with him, and this time she turns him into a Frisbee. Dizzy Devil comes up to Shirley, bawling that it's shedding season and if he spins, he'll lose all his fur. Shirley tells him to not let that fear get in his way and spin anyway; Dizzy goes ahead and spins, and sure enough, he loses all his fur. As Shirley laughs at his expense, he dresses himself with a box and walks around wearing it, which Mary Melody, Furball, Calamity Coyote, and Vinnie the Deer mistake for a new fashion trend. Fowlmouth asks Shirley for a movie date one more time, and she finally agrees so that he'll stop his begging.
Meanwhile, the Pigs are currently driving through the desert and singing "100 Bottles of Non-Alcoholic Beverage on the Wall", much to Plucky's displeasure. (When he asks why they're not singing "beer", Winnie replies "We don't drink in our family!") Plucky complains about the heat in the car and asks for some air-conditioning, but Wade won't turn it on because it "wastes gas", and Winnie won't let him roll down the windows 'cause then "people will think we can't afford air conditioning. Additionally, Wade cannot seem to stop humming "Pop Goes to the Weasel", to the point that when Plucky asks he hum something else like "Old MacDonald Had a Farm", he ends up going back to "Pop Goes the Weasel". To make matters worse, Plucky finds himself getting a shower from Uncle Stinky's sweat. The Pigs then start playing a game of "Spot the Car" to pass the time, but as Plucky finds out, their idea of this game is to yell "There's a car!" at the sight of every car that passes them (but not trucks). Then they see they're coming to a tunnel and start holding their breaths and making a wish. Plucky tries to do the same, wishing he was at Happy World Land already, but he is unable to hold his breath as long as the Pigs can. When they finally get out of the tunnel, Hamton and his parents exhale so big that their car explodes. One car-repairing scene-switch later, Plucky finds that Uncle Stinky is still holding his breath and tells him the game is over now, but Stinky's exhale is so foul that Plucky loses consciousness (and his colors, which Hamton repaints on him).
Pac-Man, Ms. Pac-Man, Pac-Baby, Blinky, Pinky, Inky, Clyde, Sue, Dinky, Buster, Babs, and Byron are still drifting down the river. Babs & Ms. Pac-Man isn't enjoying the experience, but Buster tells them to relax. During this, they pass under a rickety bridge where they see a possum kid playing a banjo. Babs, Ms. Pac-Man & Blinky think he looks scary, but Buster believes he's trying to communicate and waves to him, and gets Babs to do the same. She then begins to agree with Buster, bringing up the "romantic charm" of the possum kid's music, and starts talking sexily to Buster, but her moment is cut short when Buster tries to tell her that they're about to go over a waterfall. As they go over the fall, Superman catches them, but they tell him to get out of their movie, so he drops them back down. Buster, Byron, the Pacs & the ghosts manage to grab onto a tree branch, while Babs lands in the water below, where she encounters parodies of characters from The Little Mermaid ("oops, wrong cartoon!"). "Ariel" boots Babs back up to the surface, where Buster has also just landed, having used Byron as a parachute. Buster pumps water out of his waterlogged girlfriend and then splashes her with it, but they are then suddenly frightened by a noise. But it was just Pac-Man, Ms. Pac-Man, Pac-Baby & the ghosts climing out of the bushes were they landed. They are then scared of the presence of possums in the forest, among them the possum kid from earlier, whose name is Banjo. Pac-Man says to Banjo "Whats the big idea scaring us like that?" Banjo's kin takes the rabbits, pacs & ghosts hostage and intend to cook them. Buster engages in a "dueling banjos" act with Banjo, Pac-Man, Ms. Pac-Man, Pac-Baby & Dinky while the other possum family members start cooking Babs, and the other ghosts. They manage to get out of the pot and runs for their lives, eventually trapping the possums in a log, tying their tails together, and kicking the log into the river. Babs grabs Buster and the rest and they head back down river. Inky says he thought they were gunna be made into ghost & rabbit stew as Clyde yells at him.
Over at the beach, Elmyra, having recaptured Furball, is applying suntan lotion to him, but he manages to escape her grasp again. Elsewhere, Fifi arrives at the hotel where Johnny is staying and walks in, but the snooty doorman she encounters tosses her out. Morris (a Pac-Person) sees Fifi & asks what was she. When he finds out she is a skunk Morris runs away. Fifi enters again, this time disguising herself as Johnny's agent, Michelle Lovitze. But the doorman is not fooled, because the real Michelle Lovitz is here too - and she sits on Fifi. Pulling herself out from under Lovitz's weight, Fifi swears that it isn't over till the fat lady sings - and as if on cue, Roseanne Barr literally drops in on Fifi, singing the last lines of "The Star-Spangled Banner". Out in the dumpsters behind the hotel, Fifi weeps that she may never get Johnny's autograph now, but then sees a restaurant delivery man delivering dinner to "some Hollywood hotshot in the hotel". Thinking it's Johnny, Fifi hides in the plate, but she ends up at what appears to be a talk show convention, where we see appearances by famouse cartoon people. Fifi dashes out the window and lands in a trash basket outside the hotel, again crying over her bad luck. But then, Johnny Pew happens to pass by her, but when she asks for his autograph, he claims he does not have a pen. He says they'll find one, and in the meantime, she can carry his stuff for him.
The Pigs stop off at a drive-in restaurant for lunch at Plucky's request, but to his disbelief, he finds they've already brought their own food (mayo and cream cheese on white bread with the crusts cut off) to the drive-in. A waitress skates by to bring the Pigs the cups of water they ordered and asks if they'd like anything else. Plucky attempts to make a huge order, but Wade shuts him up and says "we're good to go." After the family gets on their way again, Plucky gets out a comic book he'd been saving to read - a mint-conditioned copy of Immature Radioactive Samurai Slugs #1 - and shows it to Hamton, but Winnie warns him that they can't have Hamton reading on family trips. Plucky dismisses this as her believing that comics rot kids' brains, but Hamton states that he actually gets carsick from reading in the car. Upon finding this out, Plucky tries to get things for Hamton to vomit into, including trying to open the door, but Hamton throws up on his comic book.
Back down river Dinky keeps whining about his ice cream cone. Inky tries to calm Dinky down by turning on the TV showing the Camping episode of SpongeBob SquarePants. Clyde has Inky turn it off.
The bunnies, Pac-People & Ghosts and Byron, meanwhile, have drifted into the Bayous and find themselves stopping in front of a Southern mansion. The bunnies come up and are greeted by a trio of
big-lipped big-breasted alligator triplets who think Buster, Pac-Baby & Dinky has come to court them. The 3 attempt to escape, but ends up bumping into their dad, who declares that now Buster, Pac-Baby & Dinky have to marry all 3 of his daughters. Babs, having watched this and gotten some giggles at Buster's expense ("I guess this'll teach Buster a thing or two about starting water fights!"), but Pac-Man tells her they have to save Buster & Pac-Baby (and Sue worries about Dinky as well), Babs gathers up some fireworks and then approaches the gators, disguised as a fireworks salesman. She rigs their gazebo with fireworks and launches it into space, but not before Buster, Pac-Baby & Dinky escape. As these 4th of July fireworks go off, the bunnies head back to their raft and continue down the river.
The Duff family is shown leaving the beach, with Elmyra upset over having lost Furball. They then drive through the Wild Safari Zoo, where Elmyra sets her sights on a cheetah and decides to go after it, despite the P.A. saying that she should not get out of the car ("so that Warner Bros. won't get sued if anyone really does this"). She comes up to the cheetah and spooks him so much he runs off with her grabbing onto his tail, eventually ripping off his fur. Elmyra, now wearing the cheetah's fur, skips around the jungle and comes upon a trio of baby lions, which she chases down. She drags the baby lions out of their hiding places and to a schoolroom she has set up, with several other captive animals as her "students". She reads to them her "favorite bedtime story", actually a book about jungle predators. As she reads, the lion cubs decide to eat the zebra captive, and then Elmyra shoves the book in the face of her gazelle captive when she finds a picture of his species in the book. Then, when she points out to them how the book cites her as the jungle's most feared predator, her imprisoned animals all race out of there. A black panther starts following Elmyra with plans to pounce her, but he ends up falling in a river and having a boulder dropped on him in his attempt. The cheetah, the lion cubs, and the panther all go to complain to their leader, a lion who sits on a throne. Elmyra comes up and the lion's subjects point her out to him, so he confronts her and roars in her face. Elmyra takes this to mean that the lion wants a haircut and gives him one that makes him look like Bart Simpson. Horrified, the lion and his subjects run out of the jungle, drag Elmyra's parents out of their car, and take off in it.
The escaping jungle cats have a brief collision with the Pig family's car. Afterward, Plucky asks Wade to stop for a drink of water, so they stop the car at a rest stop, where the Pigs suit up to go clean the public restrooms. While they're at it, Plucky attempts to get a drink from the stop's water fountain, but he's gotten himself stuck to the car seat. When he finally detaches himself, Winnie drags him away from the fountain before he can quench his thirst. Wade then turns on the radio to the K-FUDD radio station (where Elmer Fudd is apparently the DJ), which Plucky considers torture. Hamton gives him a road map to figure out how long it is till they reach Happy World Land, and Plucky uses it to figure out that at the rate they're going, they'll get to their destination on April 6, 2021. It starts raining, and the Pigs pass by a hitchhiker whom they decide to give a lift to town. Although the Pigs are more than welcome to let this stranger in the car, Plucky is immediately creeped out by him, and his suspicions are confirmed when he hears a news flash on the car radio about a psychotic, pig-hating killer on the loose who matches Mr. Hitcher's physical appearance. Plucky tries to write down the phone number to call, but Winnie turns off the radio before the whole number is stated on there. As Hitcher starts revving up the chainsaw he has concealed in his jacket, Plucky tries to warn the Pigs that this guy is the criminal the radio was talking about, but they won't listen to him. Plucky then decides to send an SOS to Shirley, hoping she'll rush to the rescue. He leaves the message in a mailbox, and it gets picked up by a mailman on a bicycle, who then bikes to a mail van (with a license plate sticker that reads "I brake for coyotes") that drives over the Road Runner.
The mailman arrives in the city and delivers Plucky's message to Shirley, but before she can read it, Fowlmouth rushes by and drags her off to the Mega Multiplex. Fifi and Johnny (who has still not signed Fifi's photo) are also at the theater, and Elmyra is also out by this theater, still looking for a new kitty to replace Furball. As Fowlmouth and Shirley arrive, it becomes evident that Fowlmouth is not particularly welcome at this theater. After he takes too long trying to decide on the snacks to get, Fowlmouth gets booted into the theater he and Shirley are seated in. He makes his way to his seat, colliding with several cameos along the way. The theater lights dim, and the screen shows a promo for the extremely loud "THUD" sound system parodying the THX sound system & deep note ("The Audience is Now Deaf"). After that is shown, Johnny comes in, with Fifi carrying his popcorn for him. The screen then shows a commercial for the Acme Gazette in which a writer for the gazette goes fishing (and doesn't notice Buster, Babs, Pac-Man, his family & the ghosts on their raft, calling for help). The movie itself then starts - Skunknophobia (which is rated "F - Not Suitable for Fowlmouth"), a flick about a man named Horatio who has a fear of skunks (one of which Johnny apparently played the part of). Fowlmouth, having seen the movie 100 times already, keeps talking through the film and won't stop giving away what happens to the other audience members. Eventually, they get sick and toss Fowlmouth into the movie itself, where even the film's characters aren't happy with his constant yapping, and they toss him right out of the theater. After Fowlmouth gets thrown out, Bimbette Skunk approaches Johnny Pew and asks for his autograph, so he gladly gives it to her, writing it on Fifi's photo. Fifi is so furious that she chastises Johnny and then throws him out of the Multiplex too, where he lands in the arms of Elmyra, who mistakes him for a cat and takes him home with her.
The Pacs, ghosts & rabbits are still drifting down the river, and Babs confides to Buster that as much as she's come to enjoy the time they've had to spend together, she really misses being back in Acme Acres. Pac-Man & the ghosts also say to Buster that they miss Pac-Land (their hometown). Suddenly, their raft collides with a riverboat, The Delta Burke, which they then climb aboard. They meet the ship's captain, Tupelo Toad, who says he doesn't take kindly to stowaways, but then offers to have them perform on the boat's stage after Babs shows him her impression of Shirley Temple (and then Lucy Ricardo). Buster tries to decline the idea, but Tupelo says he can work something out here.
Elsewhere, Mr. Hitcher makes his move and starts trying to kill Plucky with his chainsaw. Plucky tries to alert the Pigs of his predicament, but they remain blissfully unaware of the hitchhiker's homicide. Eventually, though, Wade lets Hitcher out, and he ends up sawing a telephone pole so that it drops on him, burying him into the ground. Hamton then tells Plucky that they've at last arrived at Happy World Land. After having their picture taken outside the park, they go on the monorail, where Plucky watches and admires the park's rides, all of which inflict bodily harm on the riders. To Plucky's dismay, though, the Pigs are ready to leave immediately after getting off the monorail; according to Wade, they're trying not to overdo their first trip so that they'll have more to do on their next visit.
On the Delta Burke, Buster and Babs come out to perform. But 1st Pac-Man & the ghosts preform a chomp chase. As Clyde chases Pac-Man, Pac-Baby chomps Dinky. As Dinky starts crying, Clyde scolds him for failing but Sue (who puts a new ghosts suit on the young crying ghost) tells Clyde to give Dinky a chance. Buster tries to do a stand-up based on their river trip, but Babs keeps drifting off into her impressions. Then Buster asks to have the lights turned on so they can see their audience - which, it turns out, is made up entirely of villains who've preyed on them throughout the series, including the possums and gators from earlier. The bunnies, Pacs & ghosts make a run for it, but are also chased by Tupelo and his crew. Just when they're surrounded, Byron sees them in trouble and flies into the fray, airlifting the bunnies to land nearby (and knocking ET and Elliot out on the way over). As they land Pac-Man says "Good boy Byron". Tupelo comes after them, accompanied by the possums and gators, and to make matters worse, Mr. Hitcher has come back from the grave and is now looking to kill the bunnies, Pacs & ghosts. Just when they are surrounded again, they get lifted into a tree by Banjo, who tells them that he isn't carnivorous like his kin. Hitcher starts sawing the tree down (and it crashes on Tupelo and his followers), but the bunnies, Pacs & ghosts jump into a nearby mine cart, taking Byron and Banjo with them. Hitcher follows them in another mine cart. Inky asks Hitcher if they can have a hug instead but Hithcer says no.
In the meantime, the Pigs arrive back at their house, and after the hellish car trip he has gone through, Plucky is happy to be back home. But before he can head back to his own home, the Pigs make him stay to watch their slideshow (by chaining him to the projector). It apparently goes on for days, and it's also revealed that Hamton gave Plucky's address to Hitcher. Eventually, the slideshow ends, and Plucky makes a break back for his house, with the projector still chained to his leg.
Back in the mine, Pac-Man, his family, the ghosts, Buster, Babs, Byron, and Banjo are still being pursued by Hitcher when their mine carts suddenly come out on Happy World Land's roller coaster track. They then enter a tunnel, so Buster tells his friends to hold their breath and make a wish. When they come out, they find themselves carting though the mall that Babs wished for. Upon making it out of said mall, the carts come to a fork, and Buster manages to pull the switch so that Hitcher's cart goes over a cliff and he falls into the river as Inky says "Bye bye scarey guy". Unfortunately for them, the bridge on their track is out, and they too go over the rails. Luckily, a literal plot hole opens up in the ground and drops the quartet out right over the no-longer-flooded Acme Acres ("I was wondering how those hack writers were gonna wrap things up," Babs observes). They land right in front of Acme Looniversity, where Banjo says he'd like to enroll in. As Pac-Baby gives Dinky and ice cream cone the ghost give him power pellets so Pac-Baby could chomp the other ghosts in order to save his parents. Dinky tells his cousins hes going to the beach next weekend with Pac-Baby, Buster & Babs. Babs tells Banjo there'll be plenty of time for that when school starts - which, it turns out, is right now. As the rest of their schoolmates come crowding back into the school, Babs remarks to Buster that she's upset that they spent the whole summer on the river. Buster then charms her by saying he couldn't have asked for a better summer than spending it with her - and then he squirts her face one more time. Pac-Man & Ms. Pac-Man deside to become teachers at Acme Loo & Pac-Baby & Dinky attend their as students. The film ends with the Tiny Toons characters gathering together to sing the closing number, during which Mr. Hitcher shows up to chase down Plucky again, and Babs finally gets back at Buster by dumping a whole gallon of water on him.
- Marty Ingels – Pac-Man
- Barbara Minkus – Ms. Pac-Man
- Russi Taylor – Pac-Baby
- Neil Ross – Clyde
- Chuck McCann – Blinky, Pinky
- Barry Gordon – Inky
- Susan Silo – Sue
- Charlie Adler - Buster Bunny and the Movie Theater Ticket Taker
- Tress MacNeille- Babs Bunny, Babs' Mother, Drive-thru Waitress and Big Boo
- Gail Matthius- Shirley the Loon and Sissy Boo
- Kath Soucie- Fifi La Fume, Li'l Sneezer, Little Boo and Bimbette Skunk
- Don Messick- Hamton J. Pig and the Radio Announcer
- Joe Alaskey- Plucky Duck and Tupelo Toad
- Maurice LaMarche- Dizzy Devil
- Frank Welker- Morris, Gogo Dodo, Furrball, Calamity Coyote, Little Beeper, Byron Basset, Uncle Stinky and Road Runner
- Rob Paulsen- Fowlmouth, Johnny Pew, Mr. Hitcher, Horatio and Banjo Possum
- Cree Summer- Elmyra Duff and Mary Melody
- Candi Milo- Sweetie Pie
- Jonathan Winters- Wade Pig
- Edie McClurg- Winnie Pig
- Sorrell Booke- Big Daddy Boo
- Greg Burtain- Elmer Fudd