What's the best harmless prank you pulled on someone?

A friend and I once convinced another friend of ours that I was being chatted up by and left a bar with Ron Jeremy.

The victim of the prank was running very late meeting us, so my other friend started texting her that I was talking to an old guy. The texts progressed to her being told the dude was claiming he was a famous actor and that him and I were getting very cosy. The coup de grace was telling her he said his name was Ron Jeremy and he and I were leaving together. Friend was getting alarmed messaging us that she just Googled him and he was a porn star, eventually arrived at the bar and figured out it was a prank when we were there laughing our pants off with no Ron Jeremy in sight.