The lady on the far left has been fitted with cork rump. It is recognisable due to the overly exaggerated bum that is three times the size of her head.
the 'bum', what is another way to say it without sounding too childish?
the image i'm referring to is:
Buttocks, rear end, derriere.
Pope of the Dictionary.com Forum
Back in the day when this accessory was fashionable it was referred to as a bustle.