this thread has reminded me of this story - which might be bollocks - but I won't let that stop me...
Kirk Douglas has a few kids, one of which became pretty famous and had rumpy with Catherine Zeta Jones, and one of which tried his hand at stand up back in the 80s... I can't even be bothered to google his name so will call him Todd.
Todd was on the small bar circuit, getting some laughs and packing them in when he played New York and LA, doing ok. Todd decided to try his luck across the pond in London. He's half way through a fairly unamusing routine about artificially inseminating a pet dog when he starts getting heckled... now, back in the USA he hadn't really come across this before; people pay there $4, sit down, drink their beer and laugh and clap in the right places... but there's a bloke sat a few rows back in this soho club who is openly saying "you're not very funny mate".
Todd ignores him and continues but the heckling doesn't stop. This same bloke keeps interrupting with shouts of "unfunny" or "come on, tell a joke". Todd at first doesn't reply or engage but after a while he shouts back "look buddy, I'm just trying to entertain these people here, you're ruining it for me and them". After getting the curt "fuck off" reply, he comes back with "don't you know who I am? I'm Kirk Douglas's son."
After a second or so, someone else in the audience stands up and and says "No! I'm Kirk Douglas's son." And then someone else stands up and says the same. Then another. Then a few more.
Todd left the stage and never played London again.