"The joke's on you" is an expression that normally means "You (rather than somebody else) are the victim of a joke." or "You are the one we are laughing at".
"Busted tees" is not an idiom, but it is a play on words here. A "tee" is a T-shirt. It might also be a golf tee. There is also the expression "fit to a T". The plural ("tees") also sounds like the word "