Katy Jones smiled as she watched her parents car pull out from the parking lot. Now she could have some fun with that stupid cow Amanda. Katy never got tired of reminding Amanda how much hotter she was and still just a freshmen. Walking quietly downstairs she peeked into the living room where she saw Amanda sitting on the couch facing away from her, examining something in her lap. Curious, Katy crept up behind Amanda, and with a quick motion snatched up the object in Amanda's lap. "What have we here?" Katy asked coyly, examining the strange gun. "What IS this thing? Some kind of vibrator to keep yourself company?" Amanda got up angrily "Hey give that back!" Katy smiled "Why should I? Tell me what it is first." Amanda took a step forward but hesitated, aware that Katy mustn't learn the gun's true purpose. 'it's...it's a science project from school. Please just give it back. I need it or I'll fail my class!" Katy scoffed at this. "You're a terrible lier Amanda! Come on what is it REALLY for?" Looking at the dials which read "muscle mass" and "height" Katy turned up the dials to see if anything would happen. Seeing Katy had taken her eyes off her, Amanda lunged for the gun and managed to grab hold, but Katy fought back and pulled it back towards herself. Suddenly a blast of energy shot out from the gun and into Katy. She gasped and angrily shoved Amanda to the floor. "You stupid bitch! What did that thing do to me?! If I get sick my parents will..." Her voice trailed off as she felt something within herself, raw energy flowing through her body. Katy gasped and looked down at her arms, which had begun to swell and bulge with muscle. She flexed her bicep which swelled up into a baseball sized peak and continued to get steadily larger. Moaning with delight Katy watched as her whole body expanded and lengthened, muscles growing larger and larger by the second. With a mighty hand she tore away her shirt and bra to reveal two huge tits and a rock hard eight pack. Katy laughed as she quickly overshadowed Amanda, her huge lats flaring outwards while her waist tightened. Her massive quads and calves bulged and flexed with every shift of her weight. Her muscles continued to harden and expand, becoming larger and more defined than any human on earth. "FUCK YESSSS!" Katy squealed as her growth finally subsided and she flexed every muscle in her 7ft 300lb frame. Looking down at her incredible body Katy realized that she now had what she truly craved. "Powerrrr" she purred, running her hands slowly across her incredibly huge body. Amanda still lay on the floor, unable to move or speak, staring at the amazon goddess before her with a mixture of fear and awe. What would Katy do next?