Contains spoilers
Summary — Finn's date with Flame Princess is fun, but nobody addresses the obvious problem: she's literally on fire.
Jake steals the episode, honestly. He's just having a great morning making bacon pancakes and singing to himself, and it's the most purely joyful thing in the episode. Meanwhile Princess Bubblegum strolls into their house, starts hauling away their gold, and nobody blinks. That kind of casual absurdity is Adventure Time at its best.
You do need the backstory for this one to land — Finn's long pining for Bubblegum, his whole thing with Flame Princess — or the emotional beats won't mean much. And I have one real complaint: nobody in this episode seems to care that Finn's girlfriend is made of fire. Touch her and he gets burned. Her house is permanently ablaze. If she visits his, it burns down. Bubblegum shows up with science about Flame Princess potentially exploding, which is dramatic, but the everyday physics of this relationship are a disaster and nobody mentions it. That's a big hole in a love story.
Still, I don't usually go for the romance episodes and this one won me over. Fun, funny, and Jake's pancakes alone are worth the watch.