The Andy Griffith Show Season 3 Episode 27 Barney's First Car

Andy's lovable yet gullible sidekick Barney Fife is trying to buy his first car but may in for a different ride than he thought.  The kindly old woman selling the car gives Barney her "husband's" keychain who also just so happened to be named Barney.  It is a white rabbit's foot keychain.  Barney is so nice he tries to refuse the keychain but she won't let him.

Family Guy season 13 episode 4 Brian the Closer

Brian is hiding at a hotel to avoid Quagmire because he tricked Quagmire into buying a crappy condo.  His room key with keychain be clearly seen.  He is staying in room 12.

The Simpsons season 26 episode 6 simpsorama

In this Simpsons/Futurama crossover episode the kids are putting things into a time capsule.  Milhouse puts a rabbit's foot keychain but bart didn't bring anything.  So, he puts his sandwich in there and it just so happens that the time capsule gets buried with toxic waste and the dna from Bart's sandwich combines with Milhouse's keychain to form a rabbit/Bart hybrid monster.  It causes problems in the future which sets in motion the crossover where the Simpsons meet the gang from Futurama.  It all starts with a humble keychain.