Adventure Time! has long been a major original series for Cartoon Network. Later this month, the title will return with a side story focusing on Fionna and Cake, but the showrunner has confirmed that original adventurers Finn and Jake will also appear in it.
Fionna and Cake are getting their own series, which will debut on MAX on August 31. The characters first appeared as characters spawned from the mind of the villainous Ice King and were alternate female versions of Finn and Jake. Now they will have their own adventure.
Adam Muto, showrunner of the series, went into detail about how the upcoming Adventure Time spin-off! will focus on the multiverse and confirmed that we will also see Finn and Jake in the episodes:
This show has a multiverse element to it as Fionna and Cake are from an alternate universe. We sort of build on that and use the multiverse we created on the show. So we really want to go ahead. We also want to see the contrast between Finn and Jake and Fionna and Cake. So yes, expect to see several versions of them.