Not just overexcitable, but plain ol' obnoxious. Constant interruptions, talking over the dude. I gotta wonder how, if this was his first trip there, he knew exactly what would be said?
It kinda feels like they took a lot of notes from Voltron and Avatar from the awkward wannabe-cool characters, but didn't realize why people were laughing with or at those characters.
Harry: Scientifically speaking, that isn't possible.
And then the entire class laughs.