OHHHH YEAH HALLELUJAH
Dipper panicked, floating around the room anxiously as he scolded himself outloud, while Bill Dipper, or, rather, Bipper, he supposed, checked out his new body in the mirror.
"Ooooh my god, why did I let this happen, what on Earth was I thinking?!" Dipper cried, putting his head in his hands sadly.
“Dont be so upset, Pinetree! It was inevitable, you’re dumb!” Dipper glared at Bipper angrily, floating over to him and putting his hands on his hips.
"We had a deal, Bill! What the heck?!" Bipper pulled his cheeks back examining the back of his mouth. He released them and smiled eerily at Dipper.
"Yeah? And so what? How many times have you broken promises to someone, like Summerween costuming with Mabel, or the poolcheck guy?" Bipper laughed, looking back into the mirror. Suddenly, he slapped himself, breaking out into a fit of giggles. Dipper gasped and tried to grab his hand, but of course phasing straight through him.
"No! Don’t hurt my body, c’mon man!" He groaned. Bipper smiled very widely suddenly.
"Thats right! You humans still feel pain! It’s hilarious! I wonder…" He eyed Dipper evilly and walked through him over to Mabel’s bed and looking around. Dipper followed, now very worried.
"Uh… What are you looking for?"
"Doesn’t Shooting Star knit? Aha!" Bipper found what he was looking for underneath the other twins’ pillow. Two fairly large knitting needles were in the possessed body’s hand, and Dipper would have gone pale if he wasn’t already transparent.
"Oh my… What are you doing Bill?" Dipper asked, fearful. Bipper didn’t respond, only poked the tips of the needles with an amused grin. "Dude, seriously, have mercy, don’t hurt me!" Dipper begged as Bipper lifted his shirt with one hand and pressed the cool plastic tips to his side.
"Y’know… I could just eliminate the possibility of you getting your body back ever… If you’re not around to solve the mysteries, who will?" He chuckled darkly. Dipper gaped in horror.
"W-what?! You’re crazy! Even if you did kill my body, Mabel could stop you easily!"
"Who says she can’t be just as easily persuaded as you?" Bipper snarled before plunging the needles into his skin. Dipper screamed, and Bipper gasped, letting go of his shirt and his grip on the needles, stumbling back and letting out a pained laugh. The blood oozed slowly out from around the puncture and the needles, dripping slowly down.
"HOLY HELL, BILL, YOU’RE ACTUALLY GOING TO FREAKING KILL MY BODY, PLEASE STOP!" Dipper cried, knowing that if he could, he’d be crying. Bipper continued to laugh, his face twisted in crazed amusement, and falling to his knees as he looked to the wound.
"WOW! T-that really wakes a guy up in the m-morning! I’m feeling a bit dizzy, is that bad?" Bipper snickered, smiling at Dipper slyly. Dipper flew around the room frantically.
"OH MY GOD- I am going to be dead- actually dead- truly dead- dead dead dead dead! Oh god, oh god, oh god, Mabel, oh my god…" He cried. Bipper just laughed, gripping the needles again and pulling them out and keening loudly, collapsing onto his side. The blood now flowed out quickly, the puncture wound being almost an inch and uneven. Bipper laughed maniacally, rolling onto his back and dipping his hands into the pool beginning to form on the ground. He help it up to the light, admiring it.
"You humans are so f-fragile… Tiny, and helpless. You last such a short period of time in this world- are two-dimensional when you believe yourselves to be three. You’ll all die anyways, just think of it as an early blessing. I could always leave the body and put you back in it so you could suffer the last moments of this body’s life in full detail!" Bipper hummed happily, finding the hole in his gut through the puddle of oozing red liquid on his stomach and pulling roughly at the side of it to widen it, small gasps of pain escaping his throat. Dipper was screaming again, curled in the corner and gripping his head as he wailed. He couldn’t even look, not even as Bipper rolled to his side, scooped up a good portion of blood, and began to write on the floor. Not even when a thump against the wood signaled the body giving up minutes later. Not even when Bill laughed at him after leaving the body and disappearing. Not even when his sister came running up the stairs calling his name.
Not even when he heard her scream.