20 Celebrities You Didn't Know Appeared In Rick And Morty
7. Keegan-Michael Key And Jordan Peele - The Fourth-Dimensional Beings
First Appeared In Season 2 Episode 1 - A Rickle In Time
After Rick accidentally creates a parallel dimension, he uses a time crystal to fix it but ends up creating more alternate timelines. Because of his actions, a time cop from the fourth-dimension called Shleemypants has Rick arrested.
Since Shleemypants is a wise-cracking, sarcastic, trash-talker, having Keegan-Michael Key in the role is perfect. (Also, Key is surprisingly believable as a fourth-dimensional being.)
Of course, you can't put Key in a film or series without chucking in his long-time comedy collaborator, Jordan Peele. In the post-credits scene, Shleemypants teams up with an another fourth-dimensional being, who's played by Peele, to beat up Albert Einstein, under the false impression he's Rick.