Sue pressed the trigger, anticipating watching her brother's muscles dwindle in front of her eyes. From her perch atop the flight of stairs, she stealthily observed the changes going on downstairs.
Meanwhile, on the couch, Ben felt a tingling spread throughout his entire body. He looked down, noticing something different about his body. He sat up, wondering what was going on.
And then, it happened. His chest, which was already impressive for a boy his age, swelled out even more, deepening, with real pectorals jutting out, along with shoulders the size of bowling balls.
His abdominals grew tight and hardened, becoming a formidable six pack within a minute. Ben's thighs bulged outward, the thick cords of muscle thickening and standing out. And best of all, his biceps grew even larger with each passing second. They were already pretty impressive, but now they were huge. Ben experimentally flexed one of his massive arms, delighted to see a bicep even larger than a professional bodybuilder's expand before his eyes.
A few moments later, the process ended. Ben looked his body over. The shirt he was wearing clung to his body like a second skin now, while his pants had began to split around his huge thighs and calves, exposing a little bit of muscle in the process.
"Fuck yeah!" Ben exclaimed, as everything sunk in. "I'm like the Incredible Hulk now!"
At the top of the stairs, Sue watched what had happened. She ducked around the corner, looking down at the controls. Indeed, the gun was set at (Plus) Muscle growth. She silently cursed herself, while she tried to figure out how to switch the settings.
Meanwhile, Be made his way upstairs, to find something a little more comfortable to wear. Sue heard his heavier footsteps and decided to make a mad dash for her room. After all, if he caught her holding the gun that had transformed him in the first place, what was preventing him from simply taking the gun from Sue and using it on himself?
Ben turned the corner, walking towards his bedroom, when he saw...