Rick Potion No. 9

Morty has a crush on a girl at school named Jessica. On the night of the Flu Season Dance at his school, his desire leads him to ask Rick for a love serum, and Rick acquiesces, giving him a serum derived from voles. Upon Morty giving Jessica (who, unbeknownst to Morty, has the flu) the serum, it latches onto the flu virus and goes airborne, spreading through the entire planet in a matter of minutes and causing every person not directly related to Morty to fall in love with him. In an attempt to counteract the DNA used in the original serum, Rick makes an antidote from mantis DNA, but the serum fails, instead causing the world's population to mutate into monstrous mantis-people, all of whom want to eat Morty after mating with him.

As these events transpire, Jerry, feeling insecure about his relationship with Beth, follows her to work after she is called in for a late shift. En route, Jerry finds the road blocked by the chaos created by the mantis-people; when they attempt to force Morty's whereabouts out of him, he escapes and kills them with a shotgun. Arriving at the equine hospital at which Beth works, he finds Beth cornered by her raving, infected co-worker; after Jerry kills him with a crowbar, the two reconcile their marriage.

Hiding from the infected population in the desert, Rick makes a third serum undo all the previous ones. But as the serum was amalgamated from various DNA sources, it only further mutates the world's population into barely humanoid blobs. Dubbing the monstrosities "Cronenbergs" (a reference to famous director of body horror films David Cronenberg), Rick decides the situation is beyond repair. Rather than attempt to fix the world, he scans the multiverse to find another dimension in which alternate versions of himself and Morty managed to find a solution and avert the mutation epidemic, but perished soon after. Rick and Morty enter the new reality, bury their alternate selves in the backyard and quietly assume their place. The episode ends with Morty visibly traumatized by the transpired events and his counterpart's gruesome death, set to the song "Look on Down from the Bridge" by Mazzy Star.

In a post-credits scene, Jerry, Beth, and Summer are the sole unmutated humans left in the ruined Cronenberg-infested world. Meanwhile, Cronenberg versions of Rick and Morty appear from a dimension where Cronenberg Rick accidentally turned the whole world into normal people.

Zack Handlen of The A.V. Club gave the episode of B+, liking the deconstruction of the creepiness of the love potion trope.[2] Joe Matar of the website Den of Geek liked the episode, saying that while it wasn't as funny as the previous episode, it had a wonderfully dark ending, and that he enjoyed Jerry's action hero subplot.[3] David Roa of Dead Screen loved the ending, saying that "while it was very Deus ex machina, it was still satisfying." He compared it to how people treat the planet, and just move to a new location after destroying where they live.[4] An author for the website Junkie Monkeys said that the episode was his second favorite up until that point, behind only “Anatomy Park”.[5]

Justin Roiland has called this his favorite episode of the first half of the first season, both because he thought it was paced well, and due to the fact that he loved how insane it got in the end.[6]

• "Rick Potion No. 9" on IMDb