DW and I met David Hasselhoff in the Star Gold Business Lounge in TBIT in LAX. DW got a picture with him, then turned around and started freaking out. She thought he'd walked away: he hadn't. She was really embarrassed. It gets better: He was seated a couple rows behind us on our LAX-FRA LH J flight.
We also met Wanda Sykes in US J PHL-LAX. She was in row 1, we were across the aisle in row 2. It's kind of a giveaway when you're wearing sunglasses on the plane (and you're not flying it).
Finally we met an old british actor that is on some TV show DW watches, but I can't remember his name now. We met him in LAX at baggage claim, so while not technically on the plane or in a lounge, it was in the airport.