I watched Scared Shrekless. Starring the voice talents of Mike Meyers (Austin Powers) and Cameron Diaz (Charlie's Angles; Bad Teacher).
Shrek gets in the Halloween spirit by challenging his fairytale friends to come up with scary stories for a contest. But the gang learn that they'll have to spend the night in a haunted castle before the winner is named.
I give this 2/5 stars.
This is the Shrek Halloween Special.