Nicholas "Nick" Arsenio Birch is the main protagonist and character of Big Mouth. At the beginning of the show, he is a prepubescent 13-year-old late bloomer, who lives in Westchester, New York and attended Bridgeton Middle School. He is voiced by Nick Kroll.
Nick is the youngest child of Elliot and Diane, who treat him like a little kid through hugs and affection despite Nick hates it. He is also the youngest among his siblings, Judd and Leah, and his friends Andrew, Jessi, Jay, and Missy.