Stop at traffic lights on motorbike.
Find out that bootlace has come undone.
Simultaneously find out that said bootlace has wrapped itself round footpeg, tieing foot to footpeg.
Realise that you have already started to lean bike that way, so as to ease putting foot down.
Fall off motorbike, being interrupted half way to the ground by post of aforementioned traffic light.
Have bike land on leg - still tied to footpeg, effectivly immobilising self.
Wait for grownup to help you lift motorcycle off leg, unknot lace, and then affect dignified departure.
Works for me!
A funnier variant was performed by a father of a friend, involving a kick-start lever and the flared jeans of the period.