Hi! I'm Rose, I'm really bad at introductions, and this is Pietro Maximoff, who is not as crazy as his sister (fwiw).
Pietro has the power of copying (powers, skills, knowledge, traits), which he doesn't use to its full potential or have as much control over as he pretends he does. He's also very changeable, and it can be hard to figure out who he really is, because he always seems to be different (and he likes it that way), but he usually seems to blend in one way or another. His application is
here.
Oh, and I'm not exactly a Marvel expert, so please be patient with me if you can.