It took eight seasons, but Finn finally met his mother on the Adventure Time miniseries, Islands, and after getting to know Minerva, it’s easy to see where Finn gets his urge to help people from.
After Susan Strong remembered her past life as Kara in an earlier episode, the beefy seeker takes Finn to the main human island, and while they’re flying there, we’re treated to a flashback that shows how Minerva Campbell and Finn’s dirtbag dad, Martin Mertens, met.
Minerva, who is voiced by Catastrophe’s Sharon Horgan, is a doctor — a Helper in the surviving human’s shiny, somewhat dystopic society. She meets Martin when he’s brought to her for healing after a failed escape attempt. She finds him charming, covering for Martin to save him from re-education, and the two soon fall in love. Eventually, Minerva gives birth to Finn, and they’re a happy family, for a time.
Things all go wrong when some unsavory folks from Martin’s past as a double-dealing Hider find him. Martin flees with Finn and is forced to leave his child on a floating raft that’ll eventually get to Ooo. He, meanwhile, displays some genuine heroism, taking down the monstrous guardian that keeps anything from getting on or off the island.
With both Martin and Finn missing — and Kara unable to track either of them down — Minerva is distraught. It comes at an especially bad time, because Dr. Gross accidentally unleashed a pandemic that kills off lots of humans — especially Helpers like Minerva.
Minerva, doing her best to keep everyone she can safe as the last surviving helper, uploads her brain map to the web and keeps people safe, thanks to several robo-Minervas.
This is when Finn meets her. Minerva is overjoyed to have her son back in her life and wants to keep him safe on the island… forever. All the scenes Finn showed her of his action-packed exploits in Ooo just seem too dangerous. (“You dated a bit of fire,” Minerva accurately notes.) Unwilling to let Finn leave at first, she threatens to upload everyone to the cloud, sacrificing their physical freedom for safety.
At the last moment, Finn is able to stop her plan by showing her a montage of his most helpful acts. Seeing how Finn turned out in Ooo, Minerva changes her tune. “If your world taught you to behave like that, maybe it’s not all bad,” she says.
Finn eventually leaves, though none of the other humans, save for Susan’s friend Frieda, want to depart from the island. As he heads out, Finn has a tearful VR goodbye with his mother. With only one more season of Adventure Time left after this, it’s unclear it Finn and Minerva will ever meet again. Still, this one encounter solved a major mystery for viewers — and Finn the Human.