The machine had finally been completed but the question now being posed was what would be the first test of the completed machine. You contemplated testing it on yourself but decided to hold off until you could confirm it worked as intended. An idea suddenly struck you as you realized you had your own test subject living in your house, your 3 year old son Jack, who was always so interested in what Daddy makes down in his lab. You go upstairs to find Jack and see him playing with his toys. "hey Jack, you know how you always want to help Daddy with his work, but I tell you its big boy stuff? How would you like to help daddy test a new machine he made?" "I can help? Really? You're the best daddy ever!" he exclaimed
Jack went and laid on his stomach as you aimed at him and blasted his little butt. A few seconds later you saw his pants start to get tighter as you realize you probably should've dealt with that before you blasted him but what's done is done. You watch as his backside begins to swell more and more until his pants tear off leaving him in his skin tight tighty whiteys. Before you even have a chance to react Jack tries to stand up and tears his underwear down the back. "Sorry Daddy" he apologized. You walk over and start to massage and play with your boys newly grown ass, making yours look miniscule by comparison. "this is incredible" as thought begin to flood your mind