This doesn't fit the actor/actress category, but I found it worthy of mention:
When I was a kid in school, we had these Houghton-Mifflin reading books (Signposts, Secrets, Panorama, etc.) that progressed from reading levels K-5. Well, in the book Images, I remember reading this weird yet interesting play called "The Book That Saved The Earth" by Claire Boiko.
Well, it turned out that I actually saw Claire as a contestant on Match Game '90 by accident. My jaw dropped when I heard her name mentioned. Even more surprising was that I came across an article about how she and her husband would go on game shows as contestants. Both were on MG '90, Claire was on Art Fleming's Jeopardy!, and her husband was on Concentration and Now You See It.
Again, they're not celebrities per se, but when I couldn't resist posting it.
A news article about Claire:
http://seattletimes.nwsource.com/html/nico...brodeur17m.html