‘Gravity Falls’ Alex Hirsch Explains Plans for Dipper and Mabel’s 13th Birthday

Gravity Falls creator Alex Hirsch can’t stress how important Monday night’s episode is.

“This is an extremely significant episode,” says Hirsch of the half-hour which will see Dipper and Mabel celebrate their long-awaited 13th birthdays. The episode will also see Dipper uncover a secret about Gravity Falls. We spoke to Hirsch about what else we can expect.

What does being 13 mean for Dipper and Mabel?
Both of them in theory like the idea of being taken more seriously and having more doors open to them. I think that kids all like the idea of growing up and being seen as more than just a kid. I remember being a kid and the moment I was told, “You can’t play with that toy” or “You can’t wear that ridiculous costume, here in public” it was like “Oh that’s lame.” There’s pros and cons to it.

So their birthday is definitely in the summer, they’re not celebrating it early like “Summerween”?
Their birthday is on the last day of summer, so this date has significance to both of them for both good and ill.

Does this mean they might have to leave the Mystery Shack at the end?
I can’t answer questions about what happens at the end of episodes. But the fact that you’re asking means that there’s reason to watch.

Will we get a glimpse of what past birthdays have been like for the twins?
In [the episode] “Blendin’s Game” Dipper and Mabel talk about how they’ve always had great birthdays because they’re twins and as a result it’s two kids with a birthday on the same day so they make a super awesome party. At the beginning of the episode Mabel will talk a little bit about party planning, it’s the kind of thing she loves and takes over with a manic enthusiasm that is characteristic of Mabel.

RELATED: The 6 Things we learned about Gravity Falls at New York Comic Con.

We saw in “A Tale of Two Stans” that she was kind of worried about her and Dipper’s future. Now that they’re hitting a big age, will that worry crop up again?
I think the thing that can happen when you grow up, and anybody can tell you this, everybody has a friend or a relative or somebody that they hung out with a lot and because of circumstances of life, people grow up and do different things. You kind of drift away from them, you don’t see them as much. I think that’s something that Mabel might be worried about and that’s something we might get into in this episode.

Have we seen the full extent of the geography of the town? Or are there more layers being added to it?
We sort of imagine Gravity Falls in the writers’ room to be sort of a place that grows and shrinks to fit whatever the story needs. Geography and time are sort of elastic in a comic television universe, to sort of stretch to what is coolest for the show. There’s definitely a sense that Gravity Falls has a history and that behind every waterfall and behind every tree there’s a question to be answered and some of those big questions get raised in this episode.

We haven’t heard from Bill Cipher in a while… Should we be worried?
[Laughs.] You should be worried. I advise everybody who is going to watch tonight’s episode if you have a phobia of triangles, not to watch.

What is the most exciting thing of having Grunkle Ford in the mix with the twins and Stan and Soos?
His presence brings out something different in everybody in the Mystery Shack. In Stan it brings out this sort of seething, long dormant jealousy. In Dipper it brings out the first kind of moment of respect he’s ever gotten from another adult and sort of a look at what he wishes his future could be like. The rest of the Mystery Crew are kind of pleasantly ambivalent about Ford in the way they are about the other monsters and bizarre things that happen on a weekly basis. At the end of “A Tale of Two Stans” we see that Soos calls up Wendy on the phone and tells her every single thing that’s happened in the episode and she’s already bored before he gets half way through. So she’s kind of over it.

What about Mabel?
Mabel’s first impulse when she encounters any stimulus is to be sweet and nice to it. She wants to give him the benefit of the doubt. She wants to treat him like another sweet Grunkle. He is nothing like the Grunkle she has come to love. There is a little bit of friction below the surface, but she hasn’t shown it yet.

Is Soos still in that corn maze?
Actually, to our particularly nerdy viewers, they might have decoded the code at the end of the last episode which explains that Soos, with the help of a number of friendly animals made his way back to the Mystery Shack in a plot that’s somewhat reminiscent of Homeward Bound.

Gravity Falls, Mondays, 8/7c, Disney XD.