Cracked: 'It's referred to as "keepin' 'em down" and Ferret Leggers have to keep the two thrashing, angry ferrets down their trousers for as long as possible. When the Ferret Legger can't take any more, they whip their trousers down, freeing the Ferrets, and spend the next few weeks trying to piece together their shredded pride. And genitals.'
"The ferrets are occasionally put inside the contestants' shirts in addition to their trousers. An attempt to introduce a female version of the sport—ferret busting, in which female contestants introduced ferrets down their blouses—proved unsuccessful." (Wikipedia)