Jessica Day is most well-known for being the glue that keeps the gang in loft 4D together, and she's also the one with a good head on her shoulders and keeping everyone in line. However, this teacher has a ton of quirks, and some of them are a bit immature.
From not being able to say 'penis' to literally hiding from people she doesn't want to see, Jess sometimes surprises everyone by actually being the least mature person in the loft. She gives Nick a run for his money, and there are some times to prove that this New Girl character is lacking some maturity.
When She Won't Grab Her Belongings From Spencer
In the very second episode of the series, Jess is struggling with her breakup after Spencer cheating on her. It takes a lot of convincing from the guys to get Jess to go to his house and grab the things that belong to her.
She's actually pretty evasive and childish about the whole thing. She'd prefer to run and hide and never see her things or Spencer ever again. In this episode, it was the guys who stepped up to the mature plate.
When She Sees Nick Naked
Early on in the first season, Jess walks into Nick's room - finding him naked. In response, Jess laughs and runs away from him. Not only does this make Nick super uncomfortable, but she doesn't take the whole situation in stride.
She laughs at nudity and then thinks the solution is to have Nick see her naked. She really couldn't have made this awkward situation more awkward.
When She Can't Say 'Penis'
Of all the characters, it seems strange and immature for Jess, a teacher, to have an awkward time saying the word 'penis' out loud.
Nick tries to get her to say the word, trying to prove that she can't even be mature enough to do so. It turns out, he's actually right, and Jess can't utter the word time and time again, despite her best efforts.
When She 'Parent-Traps' Her Parents
In the second season, it's revealed that Jess used to try to 'parent-trap' Bob and Joan as a kid, hoping that they would fall back in love and be together again. It also turns out that Jess isn't over that, and tries to do so again at Thanksgiving.
Cece knows what she's up to, and so do her parents. Jess trying to get her parents back together is pretty silly considering they are adults, and it is certainly one of the least mature things she's ever tried to pull off at the loft. Luckily, her parents are pretty cool people.
When She & Nick Write Down Their Thoughts
When Nick and Jess first start dating in the second season, they run into Russell out at dinner. He makes them write down their thoughts and goals of their relationship, and both of them refuse to do so and then get very secretive.
The entire beginning of their romance was a bit childish feeling, from Jess getting overwhelmed by the smallest of steps to not being able to express her feelings. It's like passing notes in grade school for these two.
When She Pays Nick's Bills
This may seem like a nice thing on the surface, but Jess really just has no boundaries. Her willingness to take things into her own hands and keep secrets might just be one of the most immature things about her. She sneaks into Nick's room and goes through his 'box,' and takes it upon herself to pay his bills.
This behavior is childish and it's actually one of the worst things she's done as a friend throughout the series. Nick might be irresponsible and also immature, but what Jess did certainly wasn't much better. An honest conversation likely would have gone far.
When She Competes For A Guy At A Wedding
In the first episode of season 4, Jess is eager to hook up at the wedding that she attends with the guys. However, there's one eligible guy, and she and another woman end up openly admitting they are competing for his attention.
Both do some pretty outrageous things, and it gets a bit ugly when they both do everything in their power to get to be the one he takes home. Finally, Jess realizes it isn't really worth it.
When She Golfs With Fawn Moscato
Near the end of the fourth season, Schmidt and Fawn Moscato have begun dating. Jess uses this to her advantage and wants to get in close with Fawn in order to get close to her contacts - attempting to get new computers for her school.
During the golf tournament, it's not just Fawn that was cringing at Jess's behavior. In fact, Jess seems not to know how to act in a professional manner with someone she wants to impress. She does her best, though.
Everything With Sam
From the first part of their relationship where she pretends to be 'Katie' to the rocky middle where she gets stuck in a car wash, Jess really doesn't seem to understand distance and respecting Sam's wishes.
She acts out, and in a very immature matter, and won't give up trying to make it up to him. Later on, she even bakes him brownies - which he definitely didn't want. Jess and Sam were a decent couple, but she has some of her worst moments with him.
When She Puts On Nick's Football Helmet
The fifth season is kind of a wild ride for Jess. While she's dating Sam, she dreams about Nick - and things get pretty awkward. So awkward, that she ends up getting Nick's football helmet stuck on her head - all because she couldn't be mature about her dream.
Plus, after this fiasco, she and Sam call it off, the sixth season also starts with Jess being unable to handle her feelings for Nick. She doesn't even know how to speak in front of him. It seems like the series plays up Jess's immaturity a bit too much sometimes.