Kirstie Alley and Patrick Swayze?!? (Plus More Secret Celebrity Affairs That Stayed Hidden for Years)

Affair: David Boreanaz and allegedly (famous Tiger Woods mistress) Rachel Uchitel

Length hidden: Roughly 5 months. Reports place the fling in late 2009/early 2010; the Bones star was busted when his mistress, reportedly Uchitel, tried to extort him. (Uchitel denied the claims of extortion.)

Affair: Let's get this one over with quickly--this year, Arnold Schwarzenegger wrote in his memoir about hooking up with actress Brigitte Nielsen on the set of Red Sonja.

Length hidden: 27 years again. (What was in the water in 1985?)

Affair: Wyclef Jean and Lauryn Hill

Length hidden: 15 years. When the Fugees broke up in 1997, rumors swirled that a volatile affair between Jean and Hill took the group down--but it wasn't until a few months ago that Jean admitted that was true.