
"Why Sheldon Cooper, PhD...
The Big Bang Theory Season 3, Episode 15

I have a PhD from Cornell University.
The Big Bang Theory Season 6, Episode 22

A PowerPoint presentation
by Sheldon Cooper, PhD."
The Big Bang Theory Season 3, Episode 15

I have a PhD in astrophysics.
The Big Bang Theory Season 10, Episode 18

and where Leonard got his PhD,
so it may have gone downhill.
The Big Bang Theory Season 10, Episode 23