Season 5 of New Girl will see the gang doing something previously unimaginable: growing up.

In the Season 4 finale, Schmidt (Max Greenfield) made the impulsive but correct decision to ask Cece (Hannah Simone) to marry him. It's a milestone in adulthood that the two of them and their friends have to reckon with, and the fifth season premiere (Tuesday at 8/7c, Fox) will see them grappling with rising to the challenge.

"There's been a lot of really funny stuff we've done over the years with them being incredibly immature, but it felt like the right moment to let them take steps forward," creator Liz Meriwether tells TVGuide.com. "We've been having an amazing time this season growing the characters, and it's resulted in more comedy, not less comedy."

Two examples of said growth: Nick (Jake Johnson) takes the reigns running the bar and Winston (Lamorne Morris) settles into his job as a cop. The show's been around for awhile now (it'll be hitting its 100th episode this season), and long-running shows are at a high risk of going stale. So letting the characters grow up is a way to keep things fresh.

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New Girl faced offscreen challenges as well, with the departure of Damon Wayans Jr. from the cast and Zooey Deschanel being absent from the show for six episodes while she's on maternity leave. But like their onscreen counterparts, everyone rose the occasion. "I'm glad Zooey took the time she needed, and it was a great challenge in the fifth season to have to do New Girl without the New Girl," Meriwether says. "I'm really proud of the episodes."

There are two episodes where it's just the four non-Deschanel members of the main cast, and the smaller cast allows the characters to deepen their relationships with each other. Meriwether is particularly excited about the growing friendship between Cece and Winston, two characters who never interacted much previously but now have the opportunity to do so.

The other four episodes without Deschanel will feature Megan Fox as a guest star. She plays a pharmaceutical rep named Reagan who sublets Jess' room while she's sequestered on jury duty. Reagan is an old friend of Cece's (they met at the 2003 MTV Beach House) whose presence forces the show to look at the characters differently. Meriwether describes her as "tough and not into the weirdness and feelings and neuroses that all of the core characters have.

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"It's been funny to have an outside perspective looking at our group and being like 'you guys are a bunch of weirdos,'" Meriweather adds.

Deschanel returns after Fox's arc, and those episodes will see Jess and Nick deal with their unresolved feelings for each other. Nick and Jess 'shippers shouldn't get their hopes up, though; Meriwether says Nick and Jess are "definitely" not together this season.

Winston will finally have a major romantic plot this season, though. He falls for his all-business partner Aly (Nasim Pedrad), and he will be spending this season trying to win her over.

But the throughline for the whole season is Schmidt and Cece's impending marriage. It begins with the engagement party and will end with the wedding. As for what that will be, however, we'll just have to wait and see.

New Girl premieres Tuesday, Jan. 6 at 8/7c on Fox.