When I broke up with Penny,
I got back into my CELLO...
The Big Bang Theory Season 4, Episode 3
...building computers
or practicing your CELLO...
The Big Bang Theory Season 8, Episode 22
Leonard, I didn't know
you played the CELLO.
The Big Bang Theory Season 1, Episode 5
This one birthday,
I came home from my CELLO lesson...
The Big Bang Theory Season 1, Episode 16
Leonard, you'll play your CELLO.
The Big Bang Theory Season 2, Episode 12