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"Time to turn you guys back." Bill smiled as he exited a triangular shaped portal.

He was a full grown adult.

The twins' stared at bill.

"My mission is to turn you guys back in the most unpainful way, right?" He asked.

"Heh, yeah I guess it was..." Dipper said, a bit sheepishly.

"Welp, guess who stole some magic napper magic?" Bill said as he cracked his knuckles.

"Do me first!" Mabel blurted out.

"Is this going to hurt?" Dipper asked.

"Don't worry, I'll be fine, not sure about you dorks though." Bill replied.

"Wait, wha-" Dipper started.

"TOO LATE!" Bill interrupted before a flash of light blinded everyone.

The deer end of Dipper started shrinking away, along with Mabel's tail that started splitting into two.

"And just because I'm nice..." Bill said as he snapped his fingers. Mabel showed up in his arms, he was carrying her bridal style.

Her scales turned into pants and there was a bit of fin left on her feet.

"Uhhhh...." Mabel said weakly.

"So you don't drown Shooting Star." Bill said, rolling his eye.

"Right. Forgot about not having gills." She said.

Dipper looked at himself. Now he was human... almost he still had a tail and ears.

"Awww, look at Dipper!" Mabel squealed, jumping out of Bill's arms to pet Dipper.

"You kids done?" Bill asked.

"Yeah." Dipper said, gently pushing Mabel away.

"Bill! Wanna help us rescue everyone else?" Mabel asked.

Bill stroked his tiny beard, thinking about it. "Sure, I'll help ya Shooting Star.... but first, wanna make a deal?"

Mabel nodded.

"Mabel, what are y-" Dipper began.

"You can keep all the magic you get from changing people back, which also covers my part of the deal. Change everyone back to normal in the least painful way possible." Mabel said.

"Then I guess it's a deal." Bill said, extending his hand that held a flame.

Mabel cautiously shook it.

"Well, I guess I'm off to take everyone's spare magic, as a bonus I'll release them too. A little tip about deal making: make sure you don't miss any small details." Bill smirked.

Before Mabel could reply, he had teleported out of there by becoming 2d and shrinking away.

"Did he just?" Mabel said.

"Give you tips on making deals? You're not the only one who found that weird..." Dipper finished for her.
==========================

Bill appeared at the end of a hallway. As the guards that were asleep in the hallways began to wake up, Bill made huge inky tentacles whip out of his fingertips and pin them against a wall, covering their mouths so they couldn't scream.

"Man, I missed magic." Bill said a bit shadily.