In Big Mouth season 5 episode 10, the show explained its menagerie of monsters (hormone and otherwise) in one of its most meta jokes to date. In the past, the series has never side-stepped being self-referential. However, in its latest fourth-wall-break, the origin of the show’s vast array of emotional and hormonal monsters was explained directly by the show’s creator Nick Kroll.
In the season finale, Kroll Show, and even Big Mouth itself. Inside, Nick Birch came face to face with the real Nick Kroll, unanimated, and playing himself.
In the scene, Kroll himself called the fourth-wall-breaking joke a “big swing,” before going on to explain that everyone deals with personal monsters like the Hate Worm, but what’s important is how people deal with them — “your monsters are you,” he explained to animated Nick. At first, the younger Nick was shocked. But the adult Nick explains to his younger cartoon counterpart that he's not right to blame the monsters for his problems, they come from inside each person and are just reflections of what people put out into the world, whether that be hate, anxiety, hormones, or even depression.
Earlier in the episode, when Nick Birch met his adult, real-world self, he asked if the show Big Mouth was just a way for Kroll to work out his issues from his adolescence. Kroll replied that the show was meant to have him and “all the other writers” work out their problems. From the introduction of this device and throughout the scene, the writer himself continually alluded to the fact that is based on Nick Kroll's real life childhood and that the series is just his (and his fellow writers') creative attempt to therapize the past. This also implies that the monsters themselves are just tools of Nick Kroll’s attempt to understand the trauma of his adolescence.
Kroll continued to push the meta elements of the series by showing his animated self the script for the episode being written as their conversation played out. This moment tied in deliberately with his later implication that neither the monsters nor the writers were to blame for bad behavior, but rather projections of Nick Birch himself.
Over the last few seasons of Big Mouth, the show’s creators have added a plethora of new monsters to the fray beyond that of Big Mouth's now-iconic Hormone Monster. There have been Hate Worms, Depression Kitties, Shame Wizards, and many more. But, perhaps, in the finale of season 5 of Big Mouth, Nick Kroll has introduced a host of new monsters, albeit sympathetic ones: Nick Birch, and the kids themselves, in a meta, self-reflective joke about the series itself.