The cause of the transformation was a beauty potion. No age regression just beautification.
Witch Hazel meant the potion for Bugs who was wearing a ugly witch mask for Halloween. So Hazel would still be the ugliest of them all.
If any one is intrested here are two original production drawings of the characters and a cel at his site.
http://members.aol.com/bruz2/broomstick_2.html