A miscevious grin spreads across your face as you pad downstairs, the slight glow of the television lighting your way. Your sister sat on the couch, popcorn in hand, completely engrossed in her show. You cast the incantation from the shadows, her eyes still fixed on the screen. Slowly but surely, her ass begins to expand outwards, now in a small bubble butt. She shifts in her seat from the change, swearing she could feel more cushion under herself. Her butt cheeks had now rounded into basketball sizes, showing so sign of stopping. She slowly began to be pushed forward off the couch by her own vastly expanding cheeks. Her eyes widened, reconizing that something was wrong. Her ass jiggled and bounced wildly behind her as she raced for her rooms full length mirror, you watching closely from behind.
She turns to the side and gasps at her inflating ass, smooth, showing no indents. Her weight now began to feel unbalanced as her ass’ large orbs had grown even larger, dwarfing her body. She hesitantly poked it and shivered at its sensitivity.