I haven't seen him this stuck since he
tried to figure out the third Matrix movie.
The Big Bang Theory Season 3, Episode 14
He recommended that I go see
the third Matrix movie...
The Big Bang Theory Season 4, Episode 7
the calculation
of nuclear MATRIX elements.
The Big Bang Theory Season 7, Episode 20
You can see the MATRIX, can't you?
The Big Bang Theory Season 1, Episode 12