I noticed this the other night when I forced my GF to watch Austin Powers. For some reason, the bit when Dr. Evil is shaking the bag of Cat Chow and singing the jingle just makes me bust out everytime I see it. That movie has grown less funny (aside from the Dr. Evil parts) each time I see it, but that always gets me.
Top Secret: The German guard on the top of the train who doesn't duck when they go under the bridge. Or; The German interrogator after they find his friend dead, impaled on a dildo. "Vee found your friend impaled on an electrical device. It took zee doctors three hours to get the smile off his face."
Dr. Strangelove: Slim Pickins on top of the atomic bomb (CLASSIC!) or the bit when they need the change from the Coca-Cola machine. "Well, sir, then you will have the answer to the Coca Cola corporation."
Blazing Saddles: "Where the white women at?" "Excuse me while I whip this out."
--Christopher