Missy Foreman-Greenwald is one of the main characters in Big Mouth, and a close friend of Andrew, Jessi and Nick. She's an emotional and geeky girl with a big heart who's relatively far behind in terms of physical development. She is also the ex-girlfriend of Andrew, and though they have not continued their relationship although it has been revealed that both of them have romantic feelings for each other.
Missy Foreman-Greenwald was born in 2004 to Monica and Cyrus (it is unknown which last name belonged to which parent) and raised in a very progressive and open-minded household in Westchester, New York. Throughout childhood, Missy was encouraged to get involved in academics (notably the sciences) and to be comfortable with her body and sexuality. At some point in her childhood, she purchased a Glow Worm (who she'd eventually name Wiggles), who she's had a fondness forever since. As seen in "Dark Side of the Boob", Missy learned the masturbate at a really young age, by humping her glow worm toy, Mr. Wiggles. Monica knew about this and she nicely told her that "'playing with Mr. Wiggles'is something we only do when we're alone in out rooms." as a polite way of keeping her from being embarassed in public.
Missy is a short, scrawny girl who's appearance would lead you to believe that she is a couple of years younger than she is in reality. She has thick curly brown hair, large, dark hazel eyes, and a medium-brown complexion. Her clothing style is comfortable as opposed to fashionable, and she usually wears navy blue overalls on top of a bright yellow shirt and matching headband. Despite her conventionally "attractive" appearance, her late start in puberty and geeky demeanor prevent her from being considered popular among the male students in her class.
Missy is a nerdy, talkative and sweet girl with a strong moral compass. Despite her awkwardness and inability to read social cues, she is very intelligent and quick at coming up with solutions. She is also a surprising romantic, constantly carried away with fantasies about her "crushes"; namely, Nathan Fillion, Gustavo and Andrew.
- Missy is mixed-race since her father is black and her mother is either white or white-passing.
- She is also half-Jewish since her mother was raised Jewish, but is no longer practicing.
- This also foreshadows that fact that her voice actor, has resigned from voicing her after doing the fourth season.
- She is a part of the Jazz Club, along with Andrew, Caleb and Lars.
- She takes Capoeira lessons, as she demonstrates to Jay in "Steve the Virgin".
- It was implied by Andrew that she was 6 months older than him. So her birthday is somewhere in December.
- As of June 24th, 2020, Missy's voice actor, Jenny Slate publicly announced that she would be retiring her role as Missy, due to herself being Caucasian and her character being Mulatto. She considered interracial voice acting to be racist and felt as though quitting her job was the right thing to do in lieu of the death of George Floyd and the Black Lives Matter political movement.      
- It is currently unknown if this will lead to the character of Missy being sidelined or written off the show or replaced with a different voice actor.