True story. Someone I know who works at a studio tells me their co-worker came back and related the story to them. Seems their co-worker was in a studio eatery and was in line to pay for their food and saw someone they knew. They called out to them by name saying 'Hi.'
The person looked at them funny, as did the second person who was with the first person. The person cautiously said 'hi' back and that was the end of the conversation.
Only later did the co-worker figure out that they in fact did not know the person they had said 'hi' to... the person had been a candidate on one of the seasons of 'The Apprentice' and it only occured (horrifically) to the co-worker a bit later while they were eating.