What's a dumbfuck's favorite condiment to put on his burger?
Re-tarter sauce.
Hey, listen up, buttercup. This joke is funny 'cause it plays on words. See, a "dumbfuck" is supposed to be stupid, right? So instead of saying "tartar sauce", which is a normal condiment, they say "re-tarter sauce." "Retard" is an offensive word for a dumb person. Get it? I had to spell it out for you like you're five. That's a real knee-slapper right there, sport.