Gravity Falls was well-known for breaking the mold of what could be considered children's television by introducing high stakes mysteries with a touch of the supernatural, paving the way for later series like The Owl House. Massively popular to this day, the show lasted only a sweet two seasons, but was never actually cancelled. So why did it end?
As Gravity Falls creator Alex Hirsch outlined in his 2015 tweet, he had always intended for the show to be short and sweet — a simple story told over a single summer. And there's good reason for a creator to end such a wildly popular show in its prime: integrity. Integrity to the plot, characters and world of the series. As Hirsch himself said, "There are so many shows that go on endlessly until they lose their original spark." By ending the show on his terms, he avoided this undesirable fate.
A key part of the show's overarching plot revolves around both the characters and the audience solving mysteries. For this reason, the show famously included hidden codes in every episode for the viewers to hunt and solve. Had the show continued past the story's natural conclusion, there would have been the potential of cancelation between seasons, thereby robbing the viewer of the mystery's solution. In the same way, the original plot and mystery of the journals may have been forgotten or pushed to the side as new mysteries and characters took the spotlight, ruining the pace of the overarching mystery.
Furthermore, the story is one of change and growing up. From an adult perspective looking back, childhood seems to have lasted but a moment, and childhood summers even less so. By ending the series at only two seasons, Hirsch kept that feeling of a fleeting adventure while allowing the characters to grow and change naturally in response to the plot. Had Gravity Falls carried on for more seasons, certainly new characters and dynamics would have been introduced, and it would have been much harder to keep the characters' base personalities and traits consistent. While they may have changed over the course of the series, they really shouldn't be completely different by the end of one summer, nor should summer go on forever.
Another issue with a long-running series is the number of characters, plots, subplots and worldbuilding points that can be easily forgotten. Everyone knows of one show where characters have forgotten their own abilities, preferences, or had some other inconsistency simply because the writers forgot about previously established canon. With so much of the world being supernatural in Gravity Falls, it would have been easy for the writers to become inconsistent like this. However, given its emphasis on codes and secrets, Gravity Falls remained remarkably consistent. With a larger series, it would be impossible to pay off every instance of foreshadowing, but because of the short nature of the show, the writers and animators were able to craft one very tightly knit narrative that satisfied viewers.
Keeping things short also allowed the writers some freedom to spend time on episodic plots, making them as fun as possible without worrying about over-establishing the characters and invalidating future plot ideas. By having codes hidden in each episode as well, it gave the team an excuse to have fun with their own work as they waited for fans to find what they had hidden. Overall, the short, mystery-filled series allowed for much more viewer engagement than just "discussion," creating a fan dynamic that was wholly unique to the show. It is a huge part of the reason why, despite ending in early 2016, the show still has a thriving fanbase.
By ending the series on his own terms, Hirsch and his team created a world that felt vibrant and full of life, with stories going on behind the scenes. Able to capture the fleeting sensation of both summer and childhood, he created an animation masterpiece with hidden content to keep coming back to for years on end.