I knew there was some very small BMX stuff but couldnt remember specifics....
Tangential anecdote. I was shopping at the Bastille market one Sunday morning and I saw a weird little folding bike with a strange seatpost - really skinny at one end with a fat bulge in the middle, then tapering to really skinny again. I stared at it for a while, completely stumped. The bulge would stop the post sliding right down into the frame, but I couldn't figure out why you'd want that, especially on a folding bike.
Then it struck me. The original post must have been stolen or damaged, and someone had stuck an oversized (22.2mm - 31.8mm - 22.2mm) handlebar into the frame as a seatpost.
I guess you had to be there.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.