Bart decides to get rid of Santa's Little Helper after he eats the bird that Bart was trying to save from dying.

!! Tropes:

* FunWithAcronyms: Milhouse uses the pigeon to send Bart a message with a [=PDF=] file. The "file" is a photograph Milhouse considers '''P'''retty '''D'''arn '''F'''unny.
* MissingMom: Nelson's mother eloped with the clown from his birthday party.
* MouseHole: In the intro, when the Simpsons entered their living room, Prof. Frink shrunk them and they ran into the hole to escape the cat.