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

Challenge accepted.
The Big Bang Theory Season 1, Episode 2

Maybe since you're so good,
he's taking his time to meet the CHALLENGE.
The Big Bang Theory Season 6, Episode 6

Really give ourselves a CHALLENGE.
The Big Bang Theory Season 8, Episode 3

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