Nathan Fillion is one of many recurring celebrity cast on hormone monsters and hormone monstresses. The series was co-created by Kroll and his real-life best friend Andrew Goldberg and is inspired by their own experiences growing up in the suburbs of New York’s Westchester County where Big Mouth is set.
The Big Mouth cast boasts tons of big names appearing in one-off or recurring roles. Westworld's Thandie Newton as Mona – a hormone monstress who latches on to Nick and Andrew’s classmate Missy (Jenny Slate/Ayo Edebiri).
Firefly.” She gets a tad carried away in her daydream and hallucinates that Jessi’s pet dog (also voiced by Fillion) is her crush and starts making out with him.
While Fillion has only appeared once in Big Mouth as Jessi’s dog, he has voiced himself in six more episodes, mostly appearing in Missy’s daydreams. One particularly hilarious season 3 episode titled “Obsessed” introduced Missy’s erotic crossover fanfiction which details Fillion’s steamy love affair with Gustavo. This is a character from her favorite racy novel The Rock Of Gibraltar who turned himself into a horse to be with his one true love.
Unfortunately, Big Mouth season 4 didn’t feature a cameo from Nathan Fillion. However, Netflix has already renewed the animation through to a sixth season so it’s possible fans will be seeing more of Nathan Fillion in Big Mouth in the not-too-distant future.