Keli laughed and spanked her ass in response to Sarah's demand. "It's your turn to be someone else's bodypart!"
She turned her attention to Joey then, and grinned wickedly. "But I think I need something to shut you up...."
Joey saw the look in Keli's eyes, but before he could do anything, Keli shouted "I wish Joey was the buttplug I'm imagining right now!"
Joey gasped as he began to shrink, his form rapidly reducing until a smooth black buttplug sat on the floor in front of Keli. Sarah, not having seen any of this (though she had, of course, heard Keli's shout) was caught by surprise when she was suddenly stuffed with the buttplug that had been Joey, muffling her attempts at protest.
Keli wiggled her hips to settle the buttplug in place, loving the feeling as much as knowing her annoying, selfish ass of a roommate was now her literal ass, and plugged up with a perv to boot! She sat down, pressing the buttplug in deeper, and pondered what to do next.