>While Adventure Time showrunner Adam Muto can't give specific updates on the Adventure Time movie or the preschool Heyo BMO spinoff, he explains that the franchise's move to Warner Bros. Animation has made development much slower.

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Although this change allows for different formats like movies and spinoffs, each project now requires a longer process of being sold and approved. He attributes the long waits to this slower development combined with projects being announced too early.

https://www.polygon.com/fionna-and-cake-season-2-adventure-time-adam-muto-interview/