Have you ever watched a particular porn clip or porn movie and noticed that a particular actor (or actress, for that matter) looked like a celebrity? It's only happened a few times for me, the most memorable one being some gangbang clip where the bottom guy (it was a DP scene) looked like Peter Gallagher (While You Were Sleeping, Mr. Deeds, House on Haunted Hill). Instant mood killer right there. I was so distracted by that guy that I couldn't get back "into" the scene and finish!