- Grover as Peter
- Big Bird as Brian
- Elmo as Chris
- Meg, Joe, Glenn, Cleveland, Jaspar, and Homer Simpson as Quarantiners
- Aloysius Snuffleupagus as Vinny
- Bert as Moe Syzslak
- Ernie as Ned Flanders
- Count von Count as Sideshow Bob
- Cookie Monster as Barney Gumble
[Brian is walking down the street, holding his stomach and looking pale.]
Brian: Oh... I feel like I'm gonna blow chunks of puppy chow!
[Brian vomits all over the steps, then collapses. Chris appears.]
Chris: Oh no, Brian has the dog flu!
[Quarantiners rush over to Brian. Peter now appears.]
Peter: The Word of the Day is Quarantine. Q-U-A-R-A-N-T-I-N-E. Quarantine.
[In the hospital, Brian is lying in bed. Doctors are examining him.]
Brian: Vinny... is that you?
Meg: Oh, he must be hallucinating.
Vinny: Hi, Brian. I'm so sorry you're sick.
Brian: I'm scared, Vinny. Thank God you can't get it since you're not real.
[Brian then dies.]
Vinny: Yeah, thank G-.
[Vinny dies, then disappears.]
Sideshow Bob: [handing out vaccines to everyone] One vaccine, a-hah-hah! Two vaccines, a-hah-hah!
[Barney eats the vaccine that Sideshow Bob gives to him]
[The show cuts to a separate bit]
Kids: One of these kids is not like the others. One of these kids is dead!
Announcer: Today's episode brought to you by the letter C.D.C.