Drawing inspiration from the movie Inception , Rick and Morty enter the dreams of Mr. Goldenfold. They descend through multiple dream layers, encountering various threats, including the Freddy Krueger-esque character Scary Terry . Viewing Options
As Morty and Rick step through the portal, they find themselves in a world filled with giant spiders and other bizarre creatures. They soon discover that the device has merged their DNA with that of the creatures in this new dimension.
The episode you're referring to is Season 1, Episode 2, titled "Rick Potion #9." The episode originally aired on December 7, 2013.