I loved it when the AI was telling you how it was going to invite all your friends to the party, but you killed the weighted companion cube and have no other friends XD The weighted companion cube was such an awesome sidekick, euthanizing it was horrible yet hilarious at the same time.
Also when the AI was trying to reason you into assuming Party Escort Submission Position and when it was like "They are eating the cake...I tried to stop them but they wouldnt listen. There might be some left if you hurry though.
And of course, when you are on that conveyor belt and see the little cake icon on the wall and you turn the corner to a freakin blazing inferno...priceless. Plus cake at the end. All in all, this game was amazing.