Rick seems to be all but resigned to not giving a shit about anything, but Morty, though understandably more jaded these days, is still a teenager who still has wants and hopes, so poking at this bit of his character remains a reliable way to eke out some development. The season premiere (which aired approximately twenty years ago, if you remember) did this and it was, like this one, one of the strongest episodes of the season. Really, “The Vat of Acid Episode” is a variation on a very similar theme as both it and “Edge of Tomorty: Rick, Die, Rickpeat” give Morty a piece of technology that allows him to tinker with his life so that he can choose whatever outcome he favors.
“The Vat of Acid Episode” fools you into thinking it’s going to be a Harmon-esque bottle episode about Rick and Morty forced to sit at the bottom of fake vat of acid for the entire runtime, but that’s a fakeout that gives way to a somber middle section told entirely without dialogue. It’s not very funny, but it’s not trying to be, as we see Morty live basically an entire fulfilling, yet harrowing life with a girlfriend he seems to care very deeply for. It’s an interesting, unique bit of storytelling, though there are a few tiny moments where I was slightly confused about what the wordless animation was trying to convey.
The ending that comes afterwards is at once devastating and hilarious. Rick’s cruelty to Morty is truly monstrous, but his stubborn, petty need to prove the worth of his vat of acid ploy is a great payoff that explains why the entire episode is named after it. It’s also devastating to see Morty lose his girlfriend again when she witnesses him jumping to what she believes to be his acidy death, but, at the same time, all the best jokes show up at the end too (e.g., Rick making Morty kiss the vat and “Oh well, he’s bones now”).
“The Vat of Acid Episode” is a standout of season four because it feels like it pushes some stuff further than we’ve seen it pushed before. Character-wise, Rick is a stone-cold evil motherfucker and Morty has to cope with overwhelming guilt and loss. As for the high-concept, sci-fi stuff, the problem of the multiverse hanging over the series as a tool for the characters to escape consequences is brilliantly turned on its head as the multiverse is used to instead punish Morty by having him deal with the consequences of his actions across the multiverse all at once. It’s not the funniest or most emotional episode, but it’s still dark enough to hurt in that Rick and Morty way and it’s a good episode because it explores the areas of the series still worth exploring.
