Ben, Gwen and Kevin

Ben, Gwen and Kevin work together to fight crime, battle the forces of evil and save the world. (And universe.)

Ben
ben is the bearer of the omnitrix. When he thought his grandpa Max was dead (but he was really in the Null Void) Ben grew up heaps. When he found out he wasn't dead and he was in the Null Void, ben turned back to his goofy old self.

Gwen
gwen is an Anodite. She can use manna to do almost anything.

Kevin
kevin is an Osmosian. He can absorb any solid substance (including energy and aliens).