Now I like it when a well known actor or familiar face pops into a movie or show for a scene or even a few seconds. Hunter S. Thompson appearing in the flashback scene of Fear & Loathing was priceless.(Holy shit, there I am!) But sometimes you see one and wonder, wtf?
For me it's Jimmy Fallon's appearance in Band Of Brothers. The episode nailed the confusion and terror of the beginning stages of the Bulge perfectly, then comes Jimmy driving up with the same shit eating grin on his face that he wears everytime his stupid mug appears on screen. Even though it's just a 30 second scene, it almost ruins the entire episode.