The Rick & Morty season 5 finale was far darker than most of season 1, but one early episode of the series set up the show’s biggest twist years in advance. Since its debut in 2013, the tone of Adult Swim’s mega-hit Rick & Morty has shifted over its five seasons. What began life as a playful, zany satire of sci-fi television and family sitcoms gradually morphed into a more self-serious, but no less fun, dissection of the two title characters and their respective neuroses.
That said, Rick & Morty was never averse to a bleak gag here and there. Season 1 boasts some of Rick & Morty’s darkest scenes despite the series generally having a goofier tone back in its early episodes. Moments like King Jellybean assaulting Morty and the grim ending of season 1, episode 6, "Rick Potion No 9," proved that Rick & Morty used to feature more standalone edgy scenes and less thoughtfully grounded moments of pathos and tragedy. However, the latter did hint at Rick & Morty’s show-shaking season 5 finale twist.
In the closing moments of season 1's "Rick Potion No 9," Rick and Morty buried their old selves after jumping between dimensions to avoid the consequences of their latest scheme. Rick commented that the duo could only jump between dimensions a few more times (even though Rick and Morty moved realities a lot more after this outing), and the line seemed like a dark, disturbing meta-joke. In retrospect, Rick’s comment also seemingly betrayed the season 5 finale’s big twist ending. When Rick & Morty’s season 5, episode 10, "Rickmurai Jack," revealed that Rick set up the Central Finite Curve in the Citadel so that he could sacrifice as many Mortys as he wanted through these sort of schemes, this proved that he was arbitrarily telling Morty that he couldn’t mess with space-time. However, Rick had been doing so for years and continued to do so until his grandson finally discovered the truth.
While Rick & Morty may seem to hate fan theories from time to time, the way this minor gag set up Rick’s big season 5 finale reveal proves that the show rewards close rewatching. It is impossible to tell whether the writers knew what Rick & Morty season 5 would reveal about Rick Sanchez and the show’s universe. Still, the ending of "Rick Potion No 9" takes on a dark new significance upon a rewatch of the early outing. This is not the only fan-adored episode that was cast in a new light by Rick & Morty’s show-shaking season 5 finale, though.
In season 4, Rick warned Morty against using a device that seemingly stopped time, allowing him to revise reality repeatedly. Morty ignored him, setting up the devastating twist that the device didn’t stop time but instead switched to a new reality, leaving the awful consequences of Morty’s actions in each dimension he left behind. The ‘Vat of Acid Episode’’s twist became tragic when Rick & Morty’s season 5 finale revealed that this was essentially the same gambit that Rick used when setting up the Central Finite Curve. The reason he wanted to warn Morty against it was so that his grandson wouldn’t end up as disillusioned and uncaring as Rick. Like the dark ending in "Rick Potion No 9," this Rick & Morty episode set up a later reveal while also working as a standalone outing for the series.