I love the fact that at the end of “Into the Bunker,” when Mabel tells Dipper she’s already written him a list of potential rebound crushes, the very next thing that happens is that Soos comes in with the laptop and says, “I’m still bummed we’re no closer to finding the Author guy.”
Because in terms of his role in the plot, the Author (initially as an abstract concept, something that Must Be Tracked Down, and later as a literal character in the story) pretty much is Dipper’s “rebound crush.”
So, for example, you have episodes that in Season 1 would have been about Dipper’s crush on Wendy vs. Mabel’s fad of the week (“Time Traveler’s Pig”), but instead they’re about Dipper’s need to find the Author vs. Mabel’s fad of the week (“Sock Opera”).
Alex Hirsch himself has said that while Dipper was always curious about solving the mysteries of Gravity Falls, it wasn’t his primary interest during Season 1, whereas now it’s an obsession that drives his character. In Season 1 we’re meant to see Dipper as a typical 12-year-old with typical 12-year-old struggles–he wants to be taller than his sister, he’s grappling with his first crush. There’s no ongoing arc yet, and the “normal town where weird supernatural stuff happens” thing is more of a setting than a plot.
But by clearly tying up the ongoing “crush on Wendy” subplot within the very first half-hour installment of Season 2, the writers send a clear message that Dipper’s priorities are about to shift to something far more dangerous.