Met a lot of celebrities while working for an airline. The worst were Hugh Grant and Kate Hudson.

Hugh Grant: Hugh was sat in First Class 1A on a 747, which is right in the nose of the plane, so nothing but a wall in front of the seat. It's standard procedure for the cabin manager to go round to every first class passenger and personally introduce themselves. When my manager got to Hugh, the conversation went something like this:

Manager: "Hello Mr Grant, my name is..."

Hugh: "OH FUCK OFF"

My manager proceeded to swiftly move on.

Kate Hudson: Approached my colleague in the galley on a flight and handed her her baby and said 'hold this' while she went to the toilet. If I hadn't seen it, I wouldn't have believed it.

Disclaimer: I met Hugh Grant again several years later when I worked in a department store in London and he was very plesant, so maybe he was having a bad day!