Doctor/Amy
You're right, that look would be all wrong on you, especially the whole helmet-thing. It would totally spoil your appeal - quite apart from the desire to assimilate and kill, obviously.
I think you just proved my point for me! Good, you can't make things any worse than they are already, so get in and have a go and you know I'll be there to back you up if you need it. You only ever have to ask.
Normal is deeply overrated. I wouldn't like it at all and I certainly wouldn't give normal a key to the TARDIS! See you in a mo - try not to break me, okay?