|“||Aw, fuck, me and my big mouth! *belch* "Big Mouth"... That's the show. That's the show! Hey, you, and you at home on the elliptical watching this. I see you. Don't you say a fucking word. Ha ha ha ha ha.||”|
—Nick Birch to viewers in The Head Push
Nicholas "Nick" Arsenio Birch is the main character and central protagonist of the Netflix original series, Big Mouth. He is a prepubescent 12-year-old late bloomer, who lives in the suburbs of New York City and attends Bridgeton Middle School. He is the youngest among his friends, Andrew, Jessi, and Jay. He is based on and voice by showrunner, Nick Kroll.
Nick Birch was born in 2005, to Diane and Elliot Birch, as the family's third born child after the oldest brother, Judd, and sole sister, Leah. Nick's parents raised him to have a kind, loving, and caring childhood using their overemotional and overly protective parenting skills. Nick's childhood was a luxury that was not given to his two older siblings, who underwent poor and mildly abusive childhoods, as their parents were still untrained in the field of parenting at the time they were being raised. Nick and his family lived in a suburban house in Bridgeton, Westchester, New York.
In a flashback from "The Planned Parenthood Show", Nick was seen in his diaper telling jokes into a microphone that his parents got him as a gift, as they looked on in happiness, with both of them smiling and holding hands with each other.
At the start of the series, Nick Birch appears as a 12-year-old boy, going to Bridgeton Middle School. His best friends are Andrew Glouberman, Jessi Glaser, and Jay Bilzerian. Nick had not yet hit puberty at the start of the show, while his best friend, Andrew, however, has already ventured far down the hormonal road of change.
In "Ejaculation", Nick and Andrew had a sleepover and Nick accidentally got an eyeful of Andrew's penis. On top of being shocked and disturbed, Nick mostly felt inferior due to Andrew's penis being significantly larger and harier than his. Later, Nick's parents explained to Nick that Andrew was going through puberty Elliot assured Nick that he was a late bloomer, much like himself when he was his age and that there was nothing to be ashamed about. However, this is exactly how Nick felt.
Nick asked out an attractive 8th-grade girl named Olivia to the school dance and although she initially accepted his request, she later dumped him at the dance, having already hooked up with a 9th-grade boy named Dylan. Heartbroken, Nick sat outside in the hallway and Jessi came by to comfort him. Nick leaned in for a kiss and Jessi went along with it.
At the end of the episode, Nick saw Maurice enter his room, during Andrew's sleepover and had the ability to communicate with him, signifying that puberty for him had officially started.
In "Everybody Bleeds", word got out about Nick and Jessi's kiss at the school dance and they were pressured into becoming a couple, despite the fact that deep down, neither of them wanted to be anything more than friends.
In "Am I Gay?", Jessi dumped Nick, which he was perfectly fine with. However, Nick went around the school, telling everybody that it was he who dumped her, which pissed her off. In the same episode, Andrew was questioning his sexuality and started to wonder if he was gay. Nick kissed him on the lips, which made him realize he wasn't actually gay.
Nick has an unusually big forehead, which is continuously doted on throughout certain times in the series. Apart from being the shortest of his friends, he also has bright blue eyes and a hook-ish nose over his upper lip. He has full lips with his front teeth being on constant display whenever he's not smiling or showing his teeth in general, which could possibly be the actual result of a dental deficiency (though not confirmed). He wears a dark blue shirt with an unbuttoned formal shirt over it, with purple pants and dark purple shoes. His appearance change is scarcely seen, with rare times of seeing him in his pajamas.
Nick is a rational, sensible, responsible young man whose confidence can take take devastating effects when confronting girls. Despite Nick being sexually knowledgeable he is not comfortable in talking or being sexual around girls, and is often critical of his best friend Andrew for being a gullible, sexually perverted and naive weirdo, which is shown in his confrontation with him at a sleepover. Throughout the series Nick's penis was publicly displayed both willingly (drunk in front of ghosts) and unwillingly (when his pants were pulled down by Lola) which made his small genitalia an extreme source of insecurity and embarrassment for him and he is often aggressive towards those who mention it. Nick himself is interested in girls; his inability to properly take initiative often leads to shortcomings and ridiculous attempts to get a girlfriend or impress Jesse.
- Andrew Glouberman - Nick and Andrew have been best friends since childhood. Andrew has been to Nick's house so much, he is considered to be part of the family. In "Ejaculation", Nick became jealous of Andrew's superior penis size, which made their friendship really awkward. In "Am I Gay?", Nick and Andrew shared a kiss, which helped the latter realize he was not gay. In "Sleepover: A Harrowing Ordeal of Emotional Brutality", the two were pitted against each other in a fight club style fight. In "Pillow Talk", Nick and Andrew went to New York City together so that Nick could get together with Roland. Andrew wanted to wear his hat to New York City but Nick made fun of him for it. In "Disclosure the Movie: The Musical!", Nick made out with Missy, which made Andrew hate him. In "Super Mouth", Andrew dumped Nick as a friend after how unkind he was to him. They parted ways but the two were still forced to spend time together because at this time, they were sent to the same summer camp.
- Jay Bilzerian - Jay is Nick's second best friend, after Andrew. Nick seems to be perfectly okay with Jay's inappropriate and misogynistic behavior, actually being able to look past it and consider him to be a friend on the same level as Andrew and Jessi. In "Sleepover: A Harrowing Ordeal of Emotional Brutality", Nick and Andrew went to Jay's house for a sleepover and ended up being tortured by all of the horrible things in their house. The duo barely escaped alive. In "Florida", Jay moved into Nick's house and although Nick was initially unhappy with it, he eventually came around to having Jay as his housemate in "How To Have An Orgasm".
- Jessi Glaser - Nick and Jessi used to just be friends but in "Ejaculation", they went to the dance together and Jessi kissed him on the lips. Since then, they've been teased as a couple by Matthew, who spread the news about their togetherness throughout the entire school. In "Everybody Bleeds", Nick and Jessi announced that they were officially a couple, simply because Matthew and the other students were pressuring them to do so. Deep down, Nick and Jessi didn't actually want to date. They just wanted to be friends so this was really awkward for them. In "Am I Gay?", Jessi kindly dumped Nick and Nick was perfectly content with this. The next day at school, Nick told everyone that he dumped Jessi, which got her really pissed off at him.
- Missy Foreman-Greenwald - Nick and Missy started off as just casual acquaintances but when Missy and Andrew started dating, she became more of a friend to him. In "Disclosure the Movie: The Musical!", they were the leading actors of the play and their characters were supposed to kiss. When they kissed on the night of the performance, they actually fell in love. This was well after Missy dumped Andrew but Andrew was still jealous of Nick because of this. Andrew gave Nick shit for this for a while but he eventually got over it. In "Super Mouth", Jessi made Nick tell the truth about not liking Missy, it pissed off both of them and turned them both against him.
- Lola Skumpy - Nick finds Lola to be rather annoying and unattractive. In "Rankings", Andrew pointed out that he was very high on Lola's list and he completely ignored this.
- Devin - Nick despises Devin because of her hateful personality but does still think she's hot. The two of them aren't outright enemies as they've never really "opposed" each other, but it's clear they don't hold each other in very high regard. In "Everybody Bleeds", Devin befriended Nick, along with Jessi, as soon as they became a couple. In "What Is It About Boobs?", Devin started dating Nick not because she actually liked him but because she was trying to get back at DeVon for dumping her for Gina. Nick seized this opportunity to kiss and make out with Devin as much as possible, really cherishing the moment.
- Shame Wizard - The Shame Wizard started harassing Nick in "The Dark Side of the Boob" when he told people about how he touched Gina's boob. In "Smooch or Share", Nick, along with all the other people The Shame Wizard was tormenting stood up to him and took him down.
- Olivia - Former Girlfriend
- Jessi Glaser - Ex-Girlfriend
- Roland - Former Girlfriend
- Gina Alvarez - Former Girlfriend
- Missy Foreman-Greenwald - Girlfriend
- Maury - Former Hormone Monster
- Rick - Former Hormone Monster
- Tyler - Former Hormone Monster
- Gavin - Briefly Hormone Monster
- Connie - Current Hormone Monster
- Nick is based on and voiced by the show creator, Nick Kroll.
- It's been explicitly mentioned many times in the series that Nick has an unreasonably small penis, which he is very self-conscious about. This was first mentioned in "Ejaculation" when he accidentally saw Andrew's much larger and hairier penis and became self-conscious about it.
- Nick's first kiss was with Jessi in the episode, "Ejaculation".
- In "Ejaculation", it was revealed that Nick's grandmother gave him a black kit-kat clock, which he has hung up on the wall of his room.
- Nick's first porno was The Italian Stallion, a videotape he watched with Andrew in "The Pornscape".
- According to Elliot's flashback in "The Planned Parenthood Show", Nick used to be interested in comedy, when he was a baby, as he was seen doing an imitation of Jerry Seinfeld. However, due to the massive amount of fabrications in this story, it is unknown if this is true to the real Nick or not.
- In "Drug Buddies", Nick and Jessi did weed for the first time.
- Nick constantly refers to himself as the nickname "Big Dick Boy", a term he coined in the episode "Drug Buddies", while he was high on weed.
- In "Dark Side of the Boob", Nick touched boob for the first time, when he touched Gina's boob under the bra while making out with her in her room.