I felt like making a review today, so here we are.
I personally hate Fionna and Cake episodes. If these were regular episodes with Finn and Jake no one would care. It's just a regular episode with a gender swap.
I love Adventure Time, but the show could have finished in 5 seasons if these stupid, sandbagging episodes didn't exist. Every episode should further the universe, not do nothing. Because of the Fionna and Cake series the rest of the lore feels a bit rushed.
Personally, if it was me who was making the show, I would make a bunch important episodes in every season. Every season equally moves towards the final episode. Also, less episodes in each season.
When the episode ends, nothing has happened. My problem is that it turns out that the whole thing is just fan fic Ice King made. Maybe they could've made it so that Fionna and Cake ARE real but from a different dimension and they meet Finn and Jake and defeat the Lich or something like that. But they don't, and they have 10 other Fionna and Cake that don't further the plot at all.
So what I think is that when the producers didn't have enough money to make actual episodes they made Fionna and Cake episodes.
5/10 Very sandbaggy.