"How many picked-on group du jour does it take to change a light bulb?"
"Knock knock! (who's there?) ..."
"A diverse group of objects walk into a bar ..."
"What happens when you cross something A with something B?", said the geneticist with a sense of humor.
Because it seemed like "really bad puns" just weren't a good fit for these. Not as if these are any less painful, though .
How many thought police does it take to change a lighbulb?
A: There *was* no light bulb. Don't you remember??
Or whatever category has stood the test of time. Stuff like that.