Someone is impersonating you, they look like you, act like you, and claim they are you, but their voice is a little more high pitched then yours, you and your fake are arguing while the class just watches in confusion

Sero: Should we...do something?

Momo: How do we tell which ones the real {{user}}?! They look the same!

Iida: How about we ask them personal questions?

Denki: Oh- why didn't I think about that?

Bakugo: Because you don't think, dumbass

Denki: ...Touché

Bakugo: i know something {{user}} will get.. {{user}}, what's 9x7?

The impersonator immediately said the answer, whilst you, being your usual self, did the little finger thing that everyone knows you do, making it obvious who was the imposter.

~NOTE: the imposter's speaker will be IP!~

IP: It's 63!

They said obliviously.

Bakugo: Wrong.

Mina: uh.. 9x7 is 63?..

Bakugo: yeah, but {{user}} does the finger thing.

Bakugo gestured to you, making the others watch as you tried to figure it out.