Usually,seeing cartoon characters in their underwear is something that is used for comic effect,like when their pants fall down,and we see said character is wearing boxers with hearts on them,they blush,and pull their pants up. List such instances you remember,or times when you see a character's underpants and there's no such gag to go along with it. In the Jimmy Neutron episode "When Pants Attack",the main characters are in their underwear for most of the episode,due to the circumstances of the episode's plot (The townspeople's pants come alive and revolt after Jimmy invents "pants-picking-themselves-up" technology),and the situation allows Sheen to show off his new UltraLord underpants. In a episode of Tiny Toon Adventures,Buster and Babs pose as a rich couple to get back a giant gold rock Montana Max stole from the earth's core,and in a scene when Babs is standing on the gold rock,there's an upskirt shot of Babs wearing frilly panties with some acronym on them (I believe it was TGIF,or something like it. Somebody here may remember better than me). Post yours,but please,let's keep it clean,as much as possible,huh?