Previously on
The Big Bang Theory...
The Big Bang Theory Season 11, Episode 15
Um, it used to be string THEORY,
now it's dark matter.
The Big Bang Theory Season 9, Episode 8
There was a scientist who had a THEORY
And James Clerk Maxwell was his name-o
The Big Bang Theory Season 8, Episode 21
Previously on
The Big Bang Theory...
The Big Bang Theory Season 7, Episode 10