
Okay, the CLUE
must be in the bag.
The Big Bang Theory Season 7, Episode 3

The sole CLUE:
"It's not what it looks like."
The Big Bang Theory Season 5, Episode 1

What was your first CLUE?
The Big Bang Theory Season 3, Episode 7

that might contain a CLUE.
The Big Bang Theory Season 7, Episode 18

I'm gonna need
another CLUE.
The Big Bang Theory Season 7, Episode 18