
...as they CHALLENGE
the preconceptions of the fields.
The Big Bang Theory Season 2, Episode 4

I have no interest in playing a game
in which I find no CHALLENGE.
The Big Bang Theory Season 3, Episode 5

Challenge them again.
The Big Bang Theory Season 10, Episode 22

I see no other option than
to CHALLENGE you to a duel.
The Big Bang Theory Season 5, Episode 17

You really want to CHALLENGE yourself,
you could learn to speak Hindi.
The Big Bang Theory Season 10, Episode 22