I think what’s really impressive about Adventure Time, ultimately, is the way it’s able to treat one or two planets and a handful of dimensions the way Doctor Who treats the entire universe. Hell, something like 80% of the show takes place on a signal continent that’s roughly the size of Australia, and the show continues to introduce new locales and characters there, each of them distinct from everything that’s come before.
The show has simultaneously allowed itself to be extraordinary diverse and yet extremely coherent. In this way, AT’s Earth is one of the best examples of worldbuilding I’ve ever seen, and I can’t wait to see it become even larger and stranger a few decades down the line.