Adam and Ian are two recurring characters in the AP series. Their main role revolves around a running gag of them getting their heads knocked together by the AP History Guy.
The first time this happens is during the second movie, where the two presumably upperclassmen were annoyed by a freshman (Mike) running through the hallway. When he insists that he is actually a sophomore, they become more enraged and chase after him. What they do not realize is that the AP History Guy is also following them, in his pursuit of Mike Dame. When the two older students finally corner Mike and prepare to beat him, Greg came up behind them and cracked their heads together with a very audible "Thunk". This noise was so loud and painful sounding that it became a piece of stock sound effect. Both young men collapsed to the floor and were not seen for the rest of the movie.
In AP3, the two upperclassman characters returned, now members of the Mike Dame Posse. When the Posse is ambushed by the AP History Guy, they attempt to fight back, but have their heads smashed together again and are knocked unconcious. They are shortly after zombified by the AP History Guy, and commanded to capture Mike Dame, chasing him throughout the halls. The Posse is unable to catch Mike, but capture Second AP History Guy and begin bringing him to the AP History Guy. Adam and Ian are turned back to normal at the end when the AP History Guy explodes, and are last seen helping the rest of the posse beat up the Second AP History Guy.
It's mentioned in AP: Apocalypse that the two died during the zombie apocalypse in between the third and fifth films. In AP: Ultimatum, Mike Dame sees the two when traveling back in time to the year 2009 and considers telling them how to avoid their deaths, only to reconsider after reliving them attempting to beat him up in the second film.
Neither movie offered them much character development, as they usually acted as comic relief in a dramatic moment. Many fans hope to learn more about these characters in future AP-related Chaos films