Goth: Becomes one after the traumatic events of the first game.
Hotter and Sexier: In the second game. To a lesser extent, this is also true of her New Game+ outfit in the first game, which is a much biggest change from her normal outfit than the other four characters get.
Master of Unlocking: His skill in the first game is in finding locks that can be picked, as well as picking them much faster than the other characters. In the second game, he's the only character who can pick locks.
The Stoner: While never outright stated, his overall mannerisms in the first game, as well as the fact that his alternate New Game+ outfit is in Jamaican/Rasta colors, seem to imply it. It's largely dropped in the sequel, though.
Sacrificial Lion: He gets killed by Leonard just after shooting Herbert Friedman.
The Smart Guy: In between teaching biology classes, he also figures out how the Mortifilia plant works.
Zombie Infectee: He was infected early on, causing him to behave more erratically as the game progresses. By the end, he is too far gone to safely use the antidote — not like it would've saved him from getting killed by Leonard anyway.
Distressed Damsel: The cafeteria level involves racing to get the lights back on while she's locked in her office.
Dumb Blonde: While she sometimes exhibits mannerisms in line with this trope, she's otherwise a subversion. Her unique skill is decrypting, which allows her to solve puzzles that the other characters can't.
Morton's Fork: One level midway through the game has Corey and Mei racing to save her. She dies whether or not you get to her in time; they'll find her dead if you don't, and if you do, they'll get separated from her and find her dead soon after.