That one is a classic. My other favorites:
The first Christmas episode where Jim says he forgot to get a gift and just grabbed something out of his closet, then it cuts to Creed and he says "Yep, that's exactly what happened."
When Andy sarcasticly thanks everyone for not telling him Angela was cheating with Dwight and Creed happily answers 'You're welcome!"
When he told Dwight and Michael the human body can live 2 minutes after getting its head cut off and Dwight says "You're thinking of a chicken." and Creed replies "What did I say?"
And his explaination of bankruptcy is awesome.