Shah Rukh Khan (though I technically didn't spot him until we were disembarking at Sahar, we were in the same cabin of the same flight).
I was flying BA First on LHR-BOM as was he, though I didn't notice until we all got up to disembark.
He was surprisingly quiet and well-behaved; no star tantrums, no fuss, no minions, nothing. He was right behind me as we exited the plane and along with everyone else, he disembarked, walked to the end of the passage, down the escalator and joined the immigration queue. He remained behind me until we reached the front of the immigration queue and he didn't make a sound the whole time.
Don't know what happened after that, since I was waiting for my friend who was being asked the usual dumb questions by the immigrationwallah, so I lost sight of our star.
Of course, this was clearly back when he was a rather well-behaved DYKWIA, rather than the DYKWIA from Wankhede.
And then there was, I was told, Tarun Tahiliani. A famous designer, though I couldn't tell him apart from any other random stranger if he came and sat on my lap. The then other half, however, does recognise all kinds of celebrities, major, minor or make-believe.
Anyway, this was again on the ground. We had just exited the terminal and were waiting for the driver to pick us up. Mr Designer was standing next to us. His driver pulled up in a Zen and our primadonna just about threw a fit.
"Why did you bring the small car? Don't you realise someone might see?"
Hahaha!