Demoted to Extra: What happens to Kamiyama as the series progresses. It was most likely intentional on the part of the author — perhaps intended as a parody of other stories where the protagonist recedes into the background due to the far more interesting and/or amusing supporting cast. Kamiyama explains why in the last episode.
Felony Misdemeanor: When asked whether he ever has done anything bad, he confesses to doing something so terrible that even his classmates are astonished. Gluing the 37,042nd domino to the ground so it wouldn't fall over when his group was trying to top the record of 37,041 dominoes in a row.
Flanderization: Kamiyama starts out as just sort of a strait-laced dork who then evolves into an uberdork whose moral fiber leads to incredibly questionable trains of thought. The author seems to suggest that Kamiyama has been this crazy since the beginning, and that it's starting to surface now that he has been among the Cromartie students for too long.
Delinquent Hair: His mohawk. It's a fake. He keeps a normal slick hairstyle under a sort of toupee on which his mohawk is placed, because his family wouldn't accept him trying to be different - so he doesn't show up at his home with his mohawk on.
The Ditz: He can't even manage a simple word problem that amounts to five minus two.
No Name Given: The author explicitly stated that the Gorilla's name is " Hiromi Go". But, it's hardly as if gorillas can introduce themselves, hence, within the story, Hiromi Go, like Freddie, is called whatever the students decided to call him. They didn't prove particularly creative in either case - though at one point everyone is convinced the gorilla is named Hajime.
An upper-class individual with aspirations of world domination, Hokuto starts at an appropriate level, taking over one high school at a time. Unfortunately, he then transfers to Cromartie, which doesn't have a structure he can easily take over.
Hey, You!: Because no one's interested enough to know Hokuto's lackey's name.
Satellite Character: Originally, though he gets more appearances and screentime than Hokuto himself in the manga. The author implied that the reason for this is how Lackey is easier to fit into any given story.
The Unreveal: Hokuto's henchman tries to reveal his name to the others. "Listen and listen good! My name is..." "Look! A meteorite just crashed into the school! "THIS ISN'T POSSIBLE!" Even when he was out on a date with a girl in volume 11 of the manga and had the chance to introduce himself to his date's friend's boyfriend, he STILL gets interrupted.
Clark Kenting: To the point that when his mask is removed, no one knows what he looks like.
Cool Old Guy: And only 30 years old. After being a hijacker, he spends the rest of the series either dealing with fitting in with a bunch of high school delinquents and (trying) to teach them important life lessons.