"In there!" Katie grabbed Tiff's hand and pulled her into a seemingly ordinary room and turned on the light. Inside was a fully stocked nursery, complete with a crib, changing table, the works!
"Oh, wow Katie, I didn't know you were interested in that sort of thing. Want me to change your diaper?" Tiff giggled and stuck her tongue out at her friend.
"Hey! I'm not 'interested' in that! I just picked a room at random!" She shot Tiff a glare and wandered into the room.
"Well, since we're here..." Tiff began, feeling her heart speed up just a bit. "We may as well experiment, right?"
"Y-you're not serious, are you?!" Katie eyed her friend like she lost her mind. "Tiffany wants to wear diapers? Aw, that's so cute!"
The two knew something strange was happening. They felt like they were acting against their own will, but it felt so good to go with the flow of things...
"Okay, Katie, I do want to wear a diaper. But so do you!" She pointed accusingly at her friend.
"A... a little bit, maybe..." Katie blushed and looked away from her friend. "So... so here's the deal: We'll BOTH experiment, but we have to promise not to tell anyone about this. Deal?"
"Deal." Tiff picked up a pack of diapers and tossed it at Katie. "You first."
"Hey, no fair! I... Hmm... Okay, I WILL go first. I'll be the first to change you!" She pounced on Tiffany and wrestled the girl's pants and panties off, while both girls giggled. Katie quickly taped a diaper onto her friend and stood up, looking smug. "Wow, you look cute. Now me!" She dropped her pants and layed back on the floor.
Tiff giggled at Katie's willingness, before carefully taping a diaper onto her. "There, all done. Now what should we-"