Lisa Simpson

Lisa is a character who pops up from time to time along with Homer Simpson.

Her apperances:

Squidward's "Dream" of Spongebob

The Plankton Who Stole Christmas (short cameo)

Squidward's Christmas Fable

It's A Simpsons World After All (mentioned)

Back to the Future

Fame and Misfortune (picture cameo)

Patrick's RoadTrip To Florida (seen as mascot for The Simpsons Ride)