Think about this: it's very possible that you know more about what Ashlee Simpson did this weekend and who Justin Timberlake is hooking up with than what you know about your own friends and family. (Scary, right?)

Yes, celebs live intriguing lives. But even if you're armed with every gossip blog and tabloid mag out there, there are still some secrets that even the most fanatical gossip girl won't uncover. Sure, we can guess what those crazy celebs are thinking, but can we ever really know what goes on inside Katie Holmes, Nicole Richie, or Britney Spears' head? No way. Grab your Ouija board -- we've got the 10 celeb mysteries that need to be solved.

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