Prologue:
Ford fired the memory gun … or at least tried to. "I'm afraid not six fingers" said a crackly voice behind everyone. He snapped his fingers and Grunkle Stan fell to the ground with a thud. At this sight Mabel collapsed and broke out into tears, "no Grunkle Stan"! She wailed for about a second before her skin started melting off of her body and she started screaming due to personal pain. Meanwhile Bill just kept laughing like this was the funniest thing he had ever seen. "Oh man you humans can't tell me this isn't funny" joked Bill. Dipper handed Ford the gun. "Ford when he's inside me I want you to shoot" whispered Dipper to Ford. "No, I can't let you do that" whispered Ford angrily, "I need to get you and your sister home to your parents, preferably in one piece. Although if that isn't possible I'll pick up the pieces I can find" finished Ford. "Ford … listen. I've spent this entire summer being taught lessons about myself and courage. If I don't do this now who, who is going to date Robbie, or cook coffee omelets, or fix golf carts" said Dipper, "no one, they will all be dead. "Dipper that is the dumbest thing I have ever heard" said Ford. "So maybe it is but you know what else is dumb, an almost 13 year old kid who has spent his life watching ghost harassers and making stupid conspiracy theories about ghosts or zombies, not willing to give up his memories of T.V. shows to save the world. You couldn't go 10 seconds without correcting Grunkle Stan in order to save the world. Honestly I don't think you ever grew up, you're still the same selfish child who gave kicked Grunkle Stan out because he banged the table and messed up your project". "Dipper I…" began Ford before Dipper ignored and walked straight past him. "Bill I want to make a deal" said Dipper. "Oh and what could you have that I could possibly want" inquired Bill. "Information" Dipper pointed to the pentagram on the floor "I can tell you where we hid the quantum destabilizer". Bill's eye changed scenes flickering as he pondered this turn of events. "Or" said Bill, "I could just take it" said Bill as he glided into Dipper's mind. As soon as he entered the whole thing burst into blue flame. "What"! Screamed Bill enraged. Dipper took a deep breath as he slowly walked to the front of the class, through the schoolyard, taking every step in this forest of his memories slowly but gradually faster. Next he passed the mystery shack, then through town, past the manatuar cave and the arcade. Dipper was now at a run. Faster and faster until he reached the cliff of his life and jumped beyond Mabel's bubble and throwing his hand into a right hook. His fist matched in line with Bill's face and destroyed the mind demon. Shattering him into millions of little shards.
...
So it turned out everything was fine Stan was alive again, the town was celebrating Dipper and Mabel's 13th birthday. Mabel's skin looked better than ever. Dipper had only lost a few memories and everything was fine. They were currently at a party to celebrate the elimination of Bill Cipher from the town. Later when they had to blow out the candles Dipper did it with joy knowing it was finally over. He blew out the candles. With his eyes closed but when he opened them he saw a black Bill cipher with a red eye wink at him. Dipper rubbed his eyes and Bill was gone. "What is it" asked Ford. "Nu- nothing, it is fine" lied Dipper.
I like to think that if Dipper hadn't lied it would have made a difference. But I don't think it would have made a difference in the end. Dipper wouldn't have pulled the trigger and Mabel wouldn't be dead.