In the second Monkey Island game, when you got to Elaine's Mansion you had to solve a riddle involving the cook - which eventually leads him to chasing your ass around the building.
The riddle itself is pretty simple and easy to solve, however, I wasn't able to figure it out because I was so busy laughing my ass off at this scene - the animation of the cook, the insults he threw at you and the mocking background music: this has to be one of my favorite moments in gaming.
And in Final Fantasy XII when you found out that...
All of Gilgamesh's legendary sword collection consists out of replicas.