"I have all sorts of trinkets, lass," said the leprechaun. "Tell me what ye want in life, and I'll see what I can do for ye."
"I just want my old boobs back," laughed Karyn, hefting her heavy breasts through her sweater.
"As it happens," said the leprechaun, "I can help ye with that. Take this ring...."
He dug a small, silver ring out of a pile of treasures with a flourish.
"When ye put this ring on, your body will magically change to fit whatever clothes ye are wearing!"
"But that can't undo the magic of the stone, can it?" asked Karyn.
"But of course it can!" replied the leprechaun. "The stone can't undo its own magic, but other magic works just fine!"
He folded the ring into Karyn's hand, and then turned to Jon. "And what about ye, lad? What is yer heart's desire?"
Jon shrugged. "I just thought the stone would help me get the things I want in life. I kinda want it back."
The leprechaun laughed. "Well, the stone won't be much use to ye, but why not take this amulet of desire?" He whipped out a small gold amulet on a chain from his pocket and started to swing it gently, like a pendulum.
"What's that?" asked Jon, following it with his eyes.
"Ye swing it in front of someone, and tell them what they want - and just like that, they want whatever ye said! Allow me to demonstrate - ye want this charm, and ye," he pointed at Karyn, "want that ring, and ye both want me to send you back home right now!"
"Yes," Jon and Karyn said simultaneously, "that's what we want!"
"Done deal, then!" the leprechaun said in a cheery voice. He put the amulet in Jon's hand, snapped his fingers, and suddenly Jon and Karyn found themselves back in Jon's room, with the leprechaun nowhere in sight.