This fourth episode of season six was, for me, the one that so far has best balanced a good story, with being funny and brings back the level of storytelling invention that we've seen in earlier seasons.
The family learn of Rick's (Justin Roiland) latest piece of alien tech, the Somnambulator, which animates their sleeping bodies and controls them to undertake preordained tasks, naturally the whole family soon wants in. Rick and Morty (Justin Roiland) both use it to exercise and gain washboard abs, Beth (Sarah Chalke) learns the trumpet, Summer (Spencer Grammer) learns Spanish and Jerry (Chris Parnell), being Jerry, turns his into a penpal. But after determining that their lot in this arrangement isn't all it could be, the night family start to rebel.
So, whilst there are definite shades of the show "Severence" to the plot of the episode, tonally it's much more similar to a horror film, particularly Jordan Peele's "Us", as the night people speak with strained voices and talk about "always having been there". There is also a mini-parody of "Avengers: Endgame" with the forging of new crockery mirroring the creation of Stormbreaker and proving one of the key themes of the episode, that Rick will do anything rather than lose face.
As I say, perhaps better than any episode in this season so far, this one felt like one that would have fit into the earlier seasons, the invention of the story, with the family fighting not to fall asleep and switching sides when they do, and it all tracking properly, makes this a plot that only "Rick and Morty" could have done and it's genuinely funny too, mixing in sight (and sound) gags with a witty script.
One of the best episodes in a while.