
Not to "Sin City" but to "SINCERE city."
The Big Bang Theory Season 9, Episode 13

And I want you to know that
that is SINCERE. I do feel bad.
The Big Bang Theory Season 9, Episode 13

Did you make the apology
as SINCERE as I would have?
The Big Bang Theory Season 9, Episode 23

A, that was not a joke,
that was a SINCERE request.
The Big Bang Theory Season 6, Episode 24

Okay. Now, see you look SINCERE
but your words are completely false.
The Big Bang Theory Season 10, Episode 6