Leah Birch is a supporting character in Big Mouth. She is the only daughter of Elliot Birch and Diane Birch, the younger sister of Judd Birch and the older sister of Nick Birch.

In the second series, she walks in on Andrew Glouberman masturbating to her swimsuit.


Leah is a Caucasian teenage girl with hip-length blonde hair that is styled on either side with a butterfly clip in that has a magenta body and tangerine wings on the right side of her head, sky blue eyes, blonde eyebrows and lemonade lips.

She wears a white sleeveless crop top, a vibrant violet skirt that has a Tiffany blue trim with a chartreuse skirt underneath her violet skirt, cerise sandals, a golden necklace, a golden belly button piercing, three golden bracelets on the right side of her wrist and a golden ring on her right index finger.


Leah is a polite and kind-hearted teenage girl who is friendly with everyone. However, if she is disrespected enough by someone, she will stop being nice and start being mean, as seen in "The Head Push", when Daniel forced her to give him a blowjob and she responded by putting his beanie full of "Cotton Candy Brandy" vomit on his head, showing him up in front of the entire party and slashing his tires. She is nice to Nick Birch who doesn't have a problem with explaining girls to him, even if that kind of stuff gets kind of sexual, as seen in "Girls Are Horny Too", when she explained what makes girls horny and in "What Is It About Boobs?", when she and Diane Birch told Nick and Andrew Glouberman that girls can appreciate each other's boobs in a non-sexual way.



Leah was born to Elliot Birch and Diane Birch and underwent a rather abusive childhood.

In "Cellsea", Diane said that whenever Leah was giving her trouble as a baby, she would just lock her in the dresser drawer until she stopped crying.

In a flashback of "The Planned Parenthood Show", Leah was seen as a toddler where she was seen playing with her dolls, while Judd Birch lit her hair on fire.

Teenage Years

Despite Leah's horrible upbringing, she turned out to be a happy and well-adjusted teenager who hasn't even proven to remember any of the bad things about her past and she currently goes to Bridgeton High School.

In "Am I Gay?", Leah mentioned that she used to date a boy named Tyler Kinney before she decided to break up with him and just be friends. Tyler got so sad and pissed off about this that he lit himself on fire in her front yard.

In "The Head Push", Leah threw a party while her parents were away where she was forced to let Nick Birch join them or else he would snitch on her. At the time, Leah was dating a theatre boy named Daniel and she took him to her room where they started to make out, but then Daniel started to push Leah's head down, signifying that he wanted her to give him a blowjob, but she refused. Daniel kept on pushing but Leah continued to refuse. Daniel got mad at her for this and so Leah dumped him and later told the entire party about what he did, which got everyone to bully him, giving him what he deserved.

In "I Survived Jessi's Bat Mitzvah", Diane Birch and Elliot Birch came home to find out about the party and punished Leah and Judd.

In "The Shame Wizard", Leah walked in on Andrew Glouberman jacking off to her swimsuit that she was equally amused and embarrassed as she laughed and both got offended at what she saw. Leah never mentioned that incident again, probably wanting to forget it, but this moment stuck with Andrew forever and even got the Shame Wizard to visit him.

In "Cellsea", Leah got a new cellphone and passed down Cellsea (Leah's old cellphone) to Nick.


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