Dipper, brainy kid that he was, tried his best to do what the turtle guy was asking, despite holding a hand to pinch his bleeding nose.

"We're people just like you that got pulled here from different universes and we're fiction to this world, too," he said in a very nasally voice. "There are lots of bad people and monsters out there trying to kill all of us for a multitude of pretty terrible reasons, so we came to save you and want to get you somewhere safe so we can explain everything that's going on."

Bim bam boom. Simple enough.