You were so busy staring at their private bits that you failed to notice their ears were longer and pointed. You did notice, however, when they suddenly started getting smaller and their skin taking on a subtle sparkle. Their faces seemed to take on a more youthful, and borderline anime-like appearance, yet their bodies maintained the maturity of the 18 year olds they were; all the while, their backs were bulging.
They let out a slight, high-pitched shout as the bulges burst open in a brief flash of glitter. Four colorful sheets streamed out of their back, waving like gossamer fabric in a breeze before flaring out and stiffening (and they weren't the only body parts in the room that stiffened). Lilly's were pink with white patterns of loops and swirls, while Alexis had green with yellow spots; and the shapes reminded you of the wings of a butterfly or... a fairy!
"Hehe! That feels much better Lil!" Alexis said.
"Indeed, Lexi." Lilly answered. Their voices were tiny, with a subtle ringing to them which didn't even echo in the locker room; difficult, but not impossible to make out, you doubt anyone beyond the thick doors or walls could hear them. They soon returned to their make-out session.
Your breathing intensified, you could hardly believe you were looking at two real live fairies making out. Lilly was kissing Alexis down her body and was about to place her lips around her nipple when her ear twitched. She paused.
"Don't stop Lilly!" Alexis whispered.
"We have company!" Lilly said. Immediately, you backed behind the lockers. "Don't bother hiding, I can still hear you breathing."
Indeed, your heavy breathing continued, not from excitement, but fear, this time. You eyed the door, thinking if you could make it out, they wouldn't dare follow, lest they risk revealing their secret to the school. But, before you could make your move, two naked fairies flew right in front of your face.
"It's a boy!" Lilly said.
"A naughty boy!" Alexis said.
"Now that shouldn't be."
"I agree, this is a girls' locker room, there should only be girls in here."
"Let's fix that!"