Just as a note, Fern did actually lose, because you're not allowed to lift your elbow in armwrestling. Only mentioning it because Uncle said they "won" from superior technology.

[7.6/10] A nice episode that splits the difference between raw fun and major arc stuff nicely. I love the conceit that it’s Finn’s 17th birthday, so he’s convinced he’s “hitting his stride” and up for whatever. The collection of gifts for him from PB, Marceline, Huntress Wizard, Starchy, and BMO are all enjoyable and particular to them, and I like that the whole Green Knight thing gets mixed up in Finn thinking it’s one of Jake’s birthday pranks. The challenge between Finn and the Green Knight is a nice bit of *Adventure Time*’s usual mix of Dungeons and Dragons-esque adventure with the mundanity of carnival games. The reveal that the whole thing is a trick by Fern and Gumbald & Co. is a nice one, that let’s the show set up big things to come (and deliver a little exposition) while couching it in a funny and wild little story. Overall, a very nice episode.