Freshman Fever
The act of a Freshman in High School thinking they're better than they really are; stronger, smarter, more athletic or popular than is truthful.
Senior 1: Haha, check out that kid over there, he's not nearly as cool as he's acting like.
Senior 2: Yep...Another kid stricken with Freshman Fever.
Senior 2: Yep...Another kid stricken with Freshman Fever.