I've had a few celebrity seatmates/flightmates:

NFL Hall of Famer Marcus Allen flying STL-LAX in F on TW (I had to ask the flight attendant who he was, since I gathered he was someone famous but didn't recognize him)

St. Louis Rams Offensive Lineman Orlando Pace on two flights STL-CLE in F on TW (Once he borrowed the sports section of my paper.. I thought about asking for an autograph, but considering the Rams lost big the day before, I thought better of it!)

Roger Ebert on AA LGA-ORD (he was in F, I was in Y)

Sen. Paul Simon on TW STL-ORD (I was in F, he was in Y!)

The Frugal Gourmet Jeff Smith on TW STL-SEA (He was in F, I was in Y)

The best story I heard about celebrity sighting was Christina Aguillera on a TWA flight... during the music video showing prior to take off, one of her videos came on. She apparently went into the lavatory and didn't come out until it was over!

Greg