There are so many funny scenes in Seinfeld that have to do with fashion faux pas.
1) George wears sweat pants and Jerry says, "do you know what message you're sending to the world when you wear sweat pants? You're saying 'I give up'. I'm miserable, so I might as well be comfortable."
- Jerry and Elaine punch George's Gortex winter coat.
3) The pink and white striped lining in Jerry's new and very expensive leather jacket.
4) Kramer sends all of Jerry's sneakers to be cleaned or something, so all he has left to wear is a pair of cowboy boots that he got as payment for doing a show. I loved Jerry's whine: "but I don't wanna be a cowboy!"
- The puffy shirt.
6) Elaine buys a horrid dress and claims the store was using "skinny mirrors".
- Kramer's extra tight jeans that made him walk like a zombie.
8) Kramer sells his suit to an annoying acquaintance of Jerry's, then realizes he has nothing to wear home. He ends up wearing Jerry's mother's fur coat.
That's all I can think of right now. If anyone can think of others, please share them!