Futurama did probably topped them all with this one:
Fry: Oh, man, this (Smell-O-Scope) is great! Hey, as long as you don't make me smell Uranus.
[He laughs.]
Leela: I don't get it.
Farnsworth: I'm sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all..
Fry: Oh. What's it called now?
Farnsworth: Urectum.
Rectum?
Damn near killed ‘im.