What?

I'm crazy

David in Hamlet... if you haven't seen it yet, you should really do so.

I'm a carp

The Doctor is obviously imitating a carp here, don't you think?

I have no idea who made this animated gif, found it online... if it is yours, please let me know and I'll give you credit for making it.

Faces

David at Comic Relief 2009... I swear, his face is made of putty or something, how can he pull off so many funny faces?

More tongue

He just doesn't stop showing us his tongue... Picture taken at Radio Times Awards

What?

He just makes the funniest faces ever

More Tongue

From Einstein and Eddington: