Third Doctor: Jo, it's all quite simple - I am he as he is me.
Jo Grant: (bemused) "And we are all together, coo coo cachoo?"
Third Doctor: What?
Jo Grant: It's a song by The Beatles.
Second Doctor: Oh? [fingering his recorder] How does it go?
Third Doctor: Oh, please be quiet!
The Three Doctors
First Doctor: So you're my replacements...a dandy and a clown.
The Three Doctors (again)
Tenth Doctor: I'm him. I'm literally him. Same man, new face. Well, new everything!
The Christmas Invasion