Tony holds Katie's mouth open with one hand and pours the contents of the vial into her mouth with the other. Katie shudders, and cum is splattered all over the floor as she reaches her orgasm. Cum soaks Tony's feet, and he tries his best to shake it off him.
The vial starts to take effect, Katie's features shrinking. But they're shrinking too much. In fact her entire body is shrinking. Tony starts to panic as Katie's body slowly begins to shrink until she looks like a pre-adolescent girl, with the addition of male genitals. Breasts that were barely A cup, and a limp, pencil thin cock with walnut sized nuts.
"Oh shit what did I do?" Tony thought. Katie sits up, having come to her senses. She rubs her head, and looks up at Tony. Even while sitting, Tony can tell Katie's barely four foot six inches. Her once voluminous hair hangs around her head wet with cum, and lifeless.
"What happened?" she asked. Tony points to the vial, and then to Katie's body. She squeals in surprise when she sees her tiny body.
"At least you're body is... more normal." Tony said, trying to console his friend.
"And look at you!" Katie said in a high voice. Tony smiled weakly, glancing at his own body. His muscles are a nice addition, but he could care less about him right now. Katie looks like she's on the verge of tears. With help, she stands on her thin legs, and takes a few breaths to calm herself.
"What are we going to do?" Katie asked. Tony looked down at her, and shrugged. The two stood in the basement, in completely different bodies than those they entered the basement in. Their clothing lay in shreds on the floor, and even if it wasn't, they wouldn't be able to fit in them. Tony's girth makes walking awkward, and Katie's body is so small and frail, Tony has to keep one arm on her shoulder to keep her from falling over.