Your inability
to successfully WOO Penny...
The Big Bang Theory Season 1, Episode 14
...that neither of you
would attempt to WOO her.
The Big Bang Theory Season 4, Episode 6
Professor Woo.
The Big Bang Theory Season 6, Episode 20
Woo!
The Big Bang Theory Season 7, Episode 6
Kripke, Professor Woo, Professor Klein,
The Big Bang Theory Season 10, Episode 16