Mabel and Dipper
Is it just me, or did Mabel and Dipper seem a bit out of character in this short? Dipper seems to have become the "walking calculator" and Mabel the stupid "catchphrase machine" that Alex Hirsch tried to avoid. Think about it. Mabel editing her brother out of her video, eating the sprinkles and ignoring Dipper's advice against them, and Dipper raining on Mabel's parade and making sarcastic, "straight-man" comments on everything she says (while he's on screen, anyway.) And it just doesn't seem to me like Mabel would be able to sit still for that long.
Greeks - The Great Robot War
The Greek page in Mabel's book told the story of an ancient war between the Greeks and the robots. The robots controlled the world for a while, forcing the humans to live underground and work in the mines, but the Greeks eventually defeated them.
Aztecs - Air Bud
The Aztec page in Mabel's book tells almost exactly the story of the Disney movie Air Bud. In the movie, a dog of the same name is adopted by a basketball team's waterboy, Josh, and eventually both play for the team. In the championship game, Air Bud sparks a comeback, and Josh makes the winning shot.
Wha-? How'd I get here?