A class clown

Idiom: A class clown


Context #1:
Jill: Have you met John, the new student from Texas?
Cathy: Yeah, he is so funny.  His first day in class he was doing an impression of President Obama and everyone was laughing so hard.
Jill: I heard about that.  I guess he has become the official class clown.

Context #2:
Tom: Man! That accounting class is so boring.
Chris: Yeah, I know.  Everyone is so serious.
Tom: We need to get a new student who can be the class clown.
Chris: Definitely!

Meaning: "class clown" is a term used to describe the student in a class who is really funny and makes people laugh.  The class clown is usually joking around and doing silly things just because that is his/her personality.