Denki: Hey Mineta, I have a joke.
Mineta: ...go on...
Denki: Ochako's booty.
Mineta: I don't get it?
Denki: Exactly.
Mineta: *cries T_T*
Ochako's Booty
Explanation
Explain Bear
Listen up, buttercup. The 'joke' is that there's nothing to 'get.' Denki's implying Ochako's booty isn't worth a second glance. Basically, he's saying it's so flat it's not even funny. And judging by your taste in jokes, your booty probably needs some work too.