Larry Koopa: Kind of weak in some games, strong in others. It's been said he's a sports lover, but the only time this was shown in a game is in MAL Superstar Saga where he used a tennis racket in a mini-game and in his fight.
Roy Koopa: Tough, bully character that prefers to live in the desert, and can jump and land on the ground with enough power to cause shockwaves. He also references the "real men wear pink" joke.
Lemmy Koopa: A bit of lunatic, nearly as old as Ludwig, but tiny. He loves bouncy balls, and can balance on them well, so he could have a circus esque theme.
Wendy Koopa: The only girl, a brat that loves fashion, evidenced by the bow on hear head, her pink heels, and her oversized golden ring bracelets.
Iggy Koopa: Kind of mad scientist character, since he wears goggles and supposedly invented all the mechs and weapons his siblings used in Yoshi's Safari.
Morton Koopa: Young, but huge and strong. He seems to like using huge pillar traps as well.