Not too bad if you have the rock

Nobody was paying attention to Fred Jr., of course, and he made his wish without anyone really listening to it. "I wish that I could turn Mom into anything I want to and nobody would notice anything wrong unless I want them to." Then he concentrated. Suddenly, his mother wasn't there any more, replaced by a picture of her that fluttered to the ground. His father and Mikey had stopped panicking. It was as if they had never even seen Fred's mother enter. Fred concentrated again. The picture turned back into his mother. And she was starting to yell something. "What is going on---" Fred didn't really want his mother to be causing trouble at the moment, but there had to be something better to turn her into than a picture. So with a thought, he changed his mother into....