Jim came to a halt in the main thoroughfare of the mall, his mind still reeling with the possibilities of the balloon. There were a number of scores he wanted to settle, but the first thing his mind turned to was self-improvement. At 12 years old, Jim was beginning to notice the teenage girls who flounced through the mall, and wanted them to notice him. But in his current state, even with the extra inch or so he'd be left with at the end of the old man's demonstration, there was no chance of that - he was a small, skinny preteen.
But I can fix that, he thought, holding the red balloon.
"Control my size and age," he said, hoping the composite attribute would work. He drew a deep breath and blew into the balloon. Immediately he felt the stretching sensation again, but this time it was different. His shirt tightened again, but this time it was focused at the shoulders and chest; his jeans began to pinch at the hips. Looking in the window of a nearby shop he saw a 14 - no, 15-year-old boy blowing into a balloon; well built for his age and rapidly becoming more so. He ran out of puff as he crossed the 16-year threshold and held the balloon shut with his thumb.
"Wow." As he had paired age with size, the balloon had not simply made him older, it had made him disproportionately taller and muscular than he would have otherwise been at this age. At 16, he was almost six foot tall, shirt riding up to expose a nice four-pack of ab muscles and tight across generous pecs. His jeans, now mid-calf, strained to contain his legs; he didn't look freakishly big, but he definitely looked like he was a serious athlete; maybe a swimmer. His package looked almost obscene; zip clearly about to give way under an endowment far in excess of the boy-junk he'd sported that morning. He wondered if it too had been enhanced further, or if a big dick was in his future anyway.
I should do something about these clothes, Jim thought, registering slightly disapproving glances from mothers with children - though no-one seemed to have clocked that he'd gained four years and 70lbs in a few minutes. Maybe it was part of the balloon's magic, or maybe he'd just got lucky. Not wanting to risk it Jim ducked into one of the public bathrooms. A man pushed past him coming the opposite direction, and Jim's finger came off the neck of the balloon for a moment. Realising the changes weren't locked in yet, he quickly tightened his grip, but even so, once he had the bathroom to himself, a check in the mirror revealed a still well-muscled but noticeably younger-looking 15-year-old, with a more innocent face and lighter hair. He considered re-upping but decided against it; 15 was still plenty old and he could easily change it again anyway.
"Release," he said, then cautiously allowed air to flow out of the balloon. His gains remained. Awesome.
Now, how to phrase it - "Control the size and age-appropriateness of my clothes." If he had it right, he should be able to inflate the balloon to the same degree he had before and have clothes that fit.
Exhaling, he felt the fabric of his jeans slip down his legs, even as the pinching at his shoulders and hips diminished. The T-shirt changed from Ben 10 through a heavy metal band logo to what looked like a vampire bunny rabbit, shifting to a Large, but remaining nicely snug on his fit body. The jeans became baggier and transitioned into cargo pants with a chain hanging from the waistband. Putting his left hand into his pocket he found his wallet had become larger, leather, and had several credit cards in it. Cool.
"Release," he said. He grinned in the bathroom mirror - a cute, muscular teen with dirty blond hair and the faint remnants of freckles across his nose. He was going to have some fun.