I wondered if it would ever make it to the London Underground and typically on what looks likely to be a freezing cold weekend, on Sunday 10th January there'll be people casually travelling around the London Underground sans trousers.
The aim is to be nonchalant and like the US riders to look as though you've just forgotten to wear trousers. The organisers say: "You can wear fun underwear if you like, but nothing that screams out, 'I wore this because I'm doing a silly stunt.' Wear two pairs of underwear if it makes you feel more comfortable. Don't wear a thong or anything else that might offend people. Our aim is to make people laugh, not piss them off."
Good luck to them, and I look forward to seeing any pictures or video on Monday, that's if TfL don't find some way of suing people for public exposure!