Deku: Hey Todoroki, are you done with your Halloween costume?
Todoroki: Yes. *comes out in a macaroni outfit*
Deku: Wha- I'm todoroni.
Bakugo: OMFG, I'm out! *blows up UA*
Macaroni Costume
Explanation
Explain Bear
Alright, listen up, you chucklehead. So, Todoroki dresses up as macaroni for Halloween, right? It's funny because it's unexpected. And the author of the joke is clearly trying to get laughs with the absurdity. Also, UA is My Hero Academia's High school. It's fiction, like you think you are!