He finished his shower and put on his clothes. He saw his shrunken sister struggling to climb onto a chair at the table. With some effort she made it up and sat as tall as her 3'8" frame allowed, her feet dangling far from the ground.
He decided to change her height again. He pushed the button, and she grew until she was two feet taller. Her body stretched out longer. Her legs grew out past the bottom of her pants until her feet touched the ground. Her belly became visible between her shirt and her pants as her torso stretched out. She was now a 5'8" tall 10-year-old girl, a full foot taller than her natural height. (And, two inches taller than her mother.) She was ridiculously skinny. What's more, she didn't notice the change at all.
She stood up from the table on her long skinny legs. And went back to try for another cookie. Of course, this time she reached the jar easily. For a moment, she looked puzzled, but then she let the thought go and enjoyed the cookie.