"Ok Sarah" said Jon "Don't do anything hasty. Let me try to figure out how this thing works."
"Alright, but if you do anything to screw this up, i'll make so small, you'll think I'm a giant."
Jon rolled his eyes. Such an original punishment, he thought. Turning his attention to the gun, he realized it was fairly simple. There was Switch that was set in the "Shrink" position, but could be flipped to the "Grow" position.
Jon pointed it at a nearby chair and pressed the trigger slightly. A red light shot out and engulfed part of the chair. Jon thought of the whole chair, and the light grew outward until it covered the full chair. It appeared that the gun was slightly psychic. Jon then pulled the trigger all the way, and the chair began to shrink to a size where 3-foot Jon could sit on it.
"So it can shrink stuff. Whoop-de-do." exclaimed Sarah sarcastically. "We want to get bigger not smaller"
"Just give me a sec, will ya" Jon said in literally the same annoyed voice.
Jon flipped the switch to Grow and put the chair back to its original size.
"YAY!" Exclaimed Sarah, jumping up and down (causing her gigantic breasts to flail around uncontrollably). "Now do me!" she commanded.
"Ok, better you than me" said Jon as he pointed it at his 1-foot tall identical twin.
"WAIT!" yelled Sarah, suddenly suspicious "What did you mean by that?"
"All I meant is that we don't know how this thing will affect people is all." Jon pushed the trigger slightly and a red light filled Sarah.
"NO!! WAIT! STOP IT!" yelled Sarah hysterically, trying to run away from the light. "You first! Do yourself first! I'm warning you! If you don't I'll make a wish."
"Ok..." said Jon, grinning slightly. He pointed the gun at his body and thought of his full body while pressing the trigger, slightly at first, then all the way.