The Beginning of the End [ Gravity Falls + Phineas & Ferb + Doctor Who ]

1984
Everything started 30 years ago when someone fell into a portal. The portal broke. A man called Stan tried to rebuild it. He spent 30 years of his life, only to help this person.

2014
Phineas and Ferb, the Fletcher brothers, and his friends builded a portal. They appear in different dimensions, but one of them was special.
They were walking in the woods when suddenly they saw a shack and went in.
A few minutes later came the owner, Stan Pines, and he knew the kids weren't from Gravity Falls.
The kids told him about the portal and he asked them for help to make his port. Two hours later went Dipper, Mabel, Soos and Wendy went to the house, the Mystery Shack. The portal was ready and they didn't understand at first who the others where or what were they doing, but at the end they understood.
A human shadow appeared in the portal. It was Stan's brother. Stan, actually Stanley, explained everything.
The kids became friends, but the old brothers, Stan and Ford, fought.
At the next day, Jeremy, Ferb's sister best friends, appeared in the woods. With his arrival they discovered a wormhole.
They weren't the only ones who knew about it. There was that one special, weird and ridiculous man. The timelord. He'll show the twins how bad could be the town if they don't win the war that Bill, who came to Gravity Falls through the wormhole, his monsters and his accomplice had started.