"Simon and Marcy" picked up a thread initially introduced last season with the finest entry in the series' history, "I Remember You," which was also the name of a show-stopping tune unveiled in the episode's climactic moments. In a touching moment of musical narrative, the song revealed that the moody goth Marceline the Vampire Queen had a history with the nutty Ice King, whose role on the show up until this point was merely as a comically inept foil to the usual protagonists, Jake the Dog and Finn the Human.
It turned out that the Ice King, originally an archeologist named Simon Petrikov, gradually lost his mind after discovering an ancient crown with magical powers in Scandinavia. When the apocalypse hit -- a period of time in the world of the show deemed The Great Mushroom War -- Simon discovered young Marceline on her own and took on a fatherly role as the two wandered through a desolate landscape.
"Simon and Marcy" detailed the evolution of that relationship while fleshing out a few other murky areas of the show's mythology. It starts innocuously enough, with modern day Marceline playing a game of basketball with the loony Ice King along with Finn and Jake, who ask Marceline why she has invited their enemy to join them. "Because I love him very much," she replies, then launches into a survival story set precisely 996 years in the past.
Up until this point, we've only had select peeks at the volume of destruction that wrecked the planet before its came together as the Land of Ooo, where the show's current colorful inhabitants live. Last season's "The Lich" showed an alternative tale of destruction and hinted at a nuclear-fueled massacre, but "Simon and Marcy" revealed a wasteland of junk barely populated by anyone other than the two characters' of the episode's title. In fact, after Simon puts on his crown and freezes a deer the duo comes across in the woods, Marceline wonders if its appearance indicates that other things live around them in the wilderness. This brief aside indicates the sheer emptiness of their environment, which epitomizes the show's ongoing ironic contrast between giddy playtime sensibilities and the dark feelings of solitude lurking beneath the surface.
The show is filled with this ongoing tension between extreme survival measures and curiously funny bits. A slapstick moment finds the duo attempting to ride a discarded motorbike into town and losing control of it; it crashes and bursts into flames below. That wry application of violent humor is matched by the next scene, when they come across a grocery store and burst through the window. "Vandalism is wrong, Marcy," Simon says, making a desperate stab at good parenting even in these dire circumstances.
From there, "Simon and Marcy" further realizes the iconography of the post-apocalyptic survival narrative to which it belongs. Up until now, the characters' placement in the scenario echoed the situation facing the man and boy in Cormac McCarthy's "The Road," but whereas that story contained demented people, this one ventures much further into the sci-fi playbook by pitting its characters against oozing green mutants who chase Simon and Marcy from every direction. Simon's conundrum is a powerful one: He has promised Marcy not to wear the crown any longer, but it's essentially the only way he can keep her safe. There's a bracing moment in which Simon nearly betrays his promise as a mutant bears down on him only to figure out an alternative plan at the last moment.
It was only a matter of time before music left a dent in this episode: "Simon and Marcy" marked the final installment co-written and storyboarded by Rebecca Sugar, who composed that heartbreaking song in "I Remember You" and has since left "Adventure Time" to work on a show of her own creation entitled "Steven Universe" (she's now the first female cartoon creator in Cartoon Network's history, according to the "Adventure Time" wiki). Though "Simon and Marcy" contained no original compositions, its use of a cheesy pop song in a gloomy situation spoke volumes about the tragedy of Simon's transition into the Ice King, a clear-cut metaphor for the onset of senility. By applying imaginary circumstances to such credible human conundrums, "Adventure Time" gets at the essence of great science fiction, which tends to imagine alternative worlds grounded in a credibility of their own making.
By the end of the episode, the fates of Simon, Marcy and the rest of the world remain uncertain. A series of quick events that, like ABC's "Lost" in its heyday, establish more questions than answers: Simon spots a pink ooze with a creepy smile that suggests a primitive version of the show's Princess Bubblegum, hinting at her mutant origins. Simon discovers the chicken soup he's been desperate to find the under-the-weather Marcy and happily feeds it to her. The whole episode he's been worried that she has come down with a fever, but is it possible that he's getting colder?
"Adventure Time" may or may not address some or all of these questions further down the line, but its willingness to contemplate them at all while sticking to its unique combination of silliness and haunting beauty routinely transforms the show into a wondrous genre experiment. More than anything else, the show illustrates the power of imagination in making dreary prospects into a challenge worth tackling time and again.