Personally, I think Adventure Time fits decently well onto Li already. Adventure time is, already, a Story about a Post-apocalyptic world in which old technology has been heavily replaced by Magic and creatively Goofy adventures, With a tone that is Both Light hearted, But on a deeper look, Holds darker and much more unique secrets to tell a meaningful story. Kinda like Li!

For Tone, I think Adventure Time fits mainly into a camp pretty similar to Mario. Like, if Mario took it's lore actually seriously, It'd be similar to adventure time, with Writing similar to Kid Icarus as well.

I am pretty much for AT's Inclusion./

I think the only thing Adventure Time brings to the table that might mesh negatively with Li are those rad neologisms the show tends to use sometimes, which isn't really the biggest deal in my opinion. I sometimes got the impression that the show was deliberately incoherent at times, but I'm unsure how much of an issue that will be when translated to writing.