GIF: JUST A BUNCH OF BARBIES (Patreon)

Amy was the most popular, prettiest girl in school, and she loved to torment the girl they all called Wendy the Weirdo. When Amy was crowned prom queen at the senior dance she knew it would be their last chance to have some fun at Wendy's expense, so she told her friends to sneak up on Wendy and pelt her with fat, juicy tomatoes. But right before Amy was about to give the signal Wendy surprised them all by climbing onstage and grabbing the mic away from the DJ.

"You assholes tortured me for four years," Wendy said. "You think everybody should be the same... Well, now you'll all be a bunch of dumb Barbie bitches, just like your queen!"

Wendy spoke an incantation and everyone started to itch, feeling strange stirrings beneath their skin, and a hot wind that smelled like flowery perfume swept through the gym and tugged hard at their clothes. The Sheckenhausen brothers ran in, raising their tomatoes high to fling them at Wendy, but then their shirts were ripped away and Todd was transformed into a topless double of Amy.  Another gust of the sweet-smelling wind and the Sheckenhausens were twins again, a pair of naked Amys with bare, bouncing breasts. With every whoosh of the wind another prom attendee was transformed, until the gym was full of naked Amys. The original Amy gasped as her glittery prom dress was ripped away to expose her, then Wendy clapped her hands and vanished with a cackle.

The wind was gone and the gym was silent now, everyone too stunned to speak. The original Amy whimpered, fumbling to cover herself, and everywhere she looked she saw her own horrified, blushing face.

(I can't say this is the best ficlet I ever wrote, but I'm kind of proud of myself for coming up with a scenario that actually fits this weird gif. I mean, some event where everybody is really itchy, and two twin guys are about to throw tomatoes when their shirts are ripped off, and one of them turns into a girl... That was a challenge! I think the original gif is from the movie Zapped 2, and it was a guy and a girl who got their shirts ripped off. I duplicated the footage of the guy to make them twins in the "before" part, and I think it turned out pretty well!)