Doctor said I can't go in the hot tub.
The Big Bang Theory Season 9, Episode 16
Oh, so now you're an astronaut
and a DOCTOR?
The Big Bang Theory Season 6, Episode 1
and you almost
became a DOCTOR?
The Big Bang Theory Season 7, Episode 14
But then again,
I don't know much about Doctor Who.
The Big Bang Theory Season 8, Episode 19
MRS. WOLOWITZ:
Paging Doctor Cutie-Pie!
The Big Bang Theory Season 4, Episode 24