'You're the Worst' Books Zosia Mamet, Lou Diamond Phillips for Season 4

You're the Worst FX - H

FXX's You're the Worst is diving deep into how a breakup impacts not only leads Jimmy (Chris Geere) and Gretchen (Aya Cash) but supporting characters Lindsay (Kether Donohue) and Edgar (Desmin Borges) as well.

Season four finds Jimmy and Gretchen coming face to face three months after he abandoned her in the Hollywood Hills after proposing marriage. In the interim, Jimmy spent that time in a retirement trailer park coming to terms with the idea that Gretchen would become his family in the wake of his father's death and what that means.

"The fun for us is to take a character that serves a function and then see what is beyond that," creator and showrunner Stephen Falk told reporters Wednesday at the Television Critics Association's summer press tour. "We're constantly trying to do that with all four characters … and trying to find the hidden depths."

To his point, season four will see Lindsay and Edgar become more of the adults in their respective friendships with Gretchen and Jimmy, who are both handling the circumstances of their breakup in different ways.

"You can see the ripples of [Gretchen's clinical depression] in almost everything. This season, you'll see Gretchen in more of a manic state than more of a depressive state in response to the breakup," Cash said. "Jimmy has not quite figured out how to deal with her response to his actions. But we're not talking about it in a way that we did in season two. But hopefully you see it reverberate."

Donohue noted that she's getting used to playing the more mature character in Lindsay and Gretchen's friendship and called the process an "interesting challenge," while noting that Gretchen is the most intimidate relationship Lindsay has ever had.

"It's exciting to explore new layers of her. … I'm not used to playing the straight man and Aya's not used to being the zany one," Donohue said. Added Cash: "Kether kept saying, 'I'm so boring in this scene,' and I kept saying, 'I'm so overacting in this scene!'"

As for how Jimmy is handling things, Geere said he's running away to punish himself for abandoning Gretchen.

"A lot of this season you always think he's bad but he's never going to be good unless he's with Gretchen, and this season is him out of his comfort zone in many ways. It highlights however hard this journey is going to be, they are perfect for each other and this is inevitable," Geere said.

Season four will see Zosia Mamet guest star as an old figure in Gretchen's life who runs a roller skating rink, while Lou Diamond Phillips will pop in for an episode as a figure from Lindsay and her sister Becca's former life. It's all part of a season that will spend a lot of time exploring all four characters as they are apart from each other.

"Having them separated is not something I relish," Falk said. "I get bummed out when my characters are all in separate stories and they don't have any overlap. That's a mid- to late-season thing. While the goal was very much to show the aftermath of the very normal rom-com breakup part of the movie and stretch that out, we quickly get them back in each other's orbits because separate, they're just four little storylines, and that's no fun."

You're the Worst is set to return Wednesday, Sept. 6, at 10 p.m. ET/PT on FXX.