Turnabout is fair Play

Tina manages to pull you out of sight of the others, causing you to pout a little.

"Come on John, I've got to reverse this!" Tina says, grabbing the book out of her bag.

"I like being this way!" you say and tackle Tina. Knocking the book out of her hand, you straddle her. "And soon, you will too."

"No, please!" Tina says.

"Vippity Boppity Bazooma!" you chant, and the changes to Tina are immediate. Her breasts expand, snapping her bra and straining at her top as her fingernails elongate, becoming pink, and her hair grows longer, turning the same platinum blonde color yours is, she lets out a giggle as the magic finishes its job, the two of you look like you could pass as sisters.

"Oooh, you where right, this is so much better," Tina says, adjusting her clothes in much the same way. "We could have a lot of fun with this."