You decide to turn yourself into a thong. It's just different enough to fuck with Kristen, you think, as you make your back end get smaller and smaller. Within seconds you're just a small sliver of fabric running down her ass, although you're still a full pair of panties in front. She must have no idea what's going on.
And she doesn't. She's in full-on panic mode. Whatever odd things may happen to you in life, your underwear doesn't just change form on you. She's sure something is wrong, and someone's controlling her underwear. But who?
The class couldn't end a moment too soon. The second the bell rings, Kristen is out the door. Her blonde hair flutters in the wind as she rushes to the science center.