Unidentified Flying Mater is the fourth episode of the spin-off of Casey jr and Friends.
At Luigi's Casa Della Tires, Guido tries to remove a hubcap from a customer's tire and ends up flinging it out of the window. It flies past Mater and Lightning McQueen, who are driving along Main Street. Mater immediately tells Lightning that it was a UFO and he knew because he'd seen one. Lightning replies with a "what?!" and Mater begins his story.
On a crystal clear night (except for several storm clouds building up behind him), Mater is driving towards a level crossing when the lights start flashing. Mater is puzzled because he cannot see any trains coming, but when he looks to his left, he sees a glowing blue buck-toothed UFO staring at him. He jumps back in fright and starts quivering when the UFO smiles at him. Mater then introduces himself and the UFO introduces himself as Mator. Mater then takes him to his "liters": a pile of oil cans. Whilst drinking, Mater teaches Mator to say, "dad-gum" and also teaches him to tip tractors and drive backwards. Mator also teaches Mater how to fly, which startles Fillmore, the Volkswagon bus. As they start flying around Willy's Butte, spotlights surround them and Mator is captured. Mater follows them and realizes that his new friend has been captured by the military forces. He then sneaks onto base using his flying technique, quick movements and a disguise to free Mator.
Lightning does not believe Mater, but Mater tells him that he was there too.
As the military forces chase Mater and Mator, Lightning McQueen joins them. Suddenly a huge UFO (presumably Mator's parent) arrives and takes the trio away. She then drops off Mater and Lightning back home before leaving.
Back in Fantasy and Fairytale Railway Traction Company Limited, Lightning still doesn't believe Mater, so Mater tries to prove he can fly. As he tries, his engine makes a horrible spluttering noise and Lightning drives away, begging him to stop. He fails to see Mater actually flying past Fillmore and Sarge. Fillmore, dumbstruck gasps, "Far out!"
In the final scene, Mater meets Mator up in space and they fly away together.
- Lightning McQueen
- Corporal Kim
- Captain Munier
- Scientist Pitties
- Mator's Mother
- Susie the Little Blue Coupe (Cameo)
- Bertil the Magic School Bus (Cameo)