Each episode of Rick and Morty is a treasure unto itself. Drawing upon co-creator Dan Harmon’s penchant for cultural references, coupled with co-creator Justin Roiland’s skill for characters, the cartoon has fun in all kinds of ways. Its sci-fi angle and smart humor make it the kind of cartoon you only wished you’d experienced on Saturday mornings as a kid.

As if it’s not enough that the show’s central characters comprise a well-rounded (if dysfunctional) family backbone that allows each episode to go off into worlds unknown, there are some fabulous guest stars to boot. The show has had all manner of comedian take part in its off-the-wall fun, including David Letterman, David Cross, Dana Carvey, Nathan Fielder and Gary Cole. There have been some legendary appearances over the course of the show’s first two seasons. Here are the ten best guest stars to appear on Rick and Morty.

Herzog voices the famed alien civil rights leader Shrimply Pibbles in “Interdimensional Cable 2: Tempting Fate,” which plays off the success of the first season’s cable-hopping episode. After arriving in a space hospital with a serious bacterial infection, Jerry recovers only to learn that doctors want to transplant his penis to save the alien equivalent of Mahatma Gandhi. Herzog’s part airs on the short side, and yet hearing the famed German director’s realist bordering on nihilist voice play an alien in need of a penis transplant remains a memorable bit. With such classic lines as, “I’ve dwelt among the humans. Their entire culture is built around their penises,” Herzog’s appearance is one for the storybooks.

In “Something Ricked This Way Comes,” Jerry wants to help Morty with his model of the solar system, only to discover from his son that Pluto is no longer a planet. Voicing disbelief bordering on anger earns Jerry and Morty a one-way ticket to Pluto, where Jerry becomes something of a legend for defending the “planet.” Maybe there’s something about Fulcher’s voice that conveys immediate hilarity, or maybe it’s the fact that as King Flippy Nips—King of Pluto—he wears the most outrageous smile, but Fulcher serves as the perfect madcap alien king, especially with his famous line, “Pluto’s a fucking planet, bitch!”

The other half of the storyline in “Something Ricked This Way Comes” pits Rick against one of his more crafty foes. When Summer gets a part-time job working for the Devil, Rick immediately takes a disliking to the man. That may have more to do with the fact that his shop gives away things for free, but only because they’re cursed. “A price for everything,” the Devil tells customers. Voiced by Molina, who gives the devil a bit of crackling ne’er do well charm, this was one of the more clever foes Rick faced off against, least of which because his least favorite grandchild got caught in the middle of their rivalry.

When his grandkids mess with time and split it into multiple trajectories in “A Rickle in Time,” Rick gets a visit from a time cop tasked with keeping things in order. The Fourth Dimensional Being, who just so happens to look like a giant testicle, also has little patience for dealing with backtalk. Known for playing characters with big reactions, Key’s exasperated screeches and tell-it-like-it-is attitude create the ideal omniscient time traveling alien who just wants to set things right. It only adds to the episode when later the Fourth Dimensional Being meets up with his partner, voiced by Jordan Peele.

“Total Rickall” takes on a new kind of antagonist: an alien species that infiltrates the family’s home by creating false memories and therefore false characters to perpetuate those memories. Enter: Sleepy Gary. In this new scenario with ever-expanding characters and plot points, he’s Beth’s husband while Jerry takes a backseat as the family friend. Sleepy Gary is the kind of sweet, considerate and mild-mannered man to attract both both Beth and Jerry. Walsh’s soothing voice lends Sleepy Gary the pathos necessary to pull off this hilarious romantic storyline.

When Earth gets tapped to perform in an intergalactic talent show, who better to call than Rick and Morty? And that’s just what happens in “Get Schwifty.“ Legendary actor Keith David has a voice well suited to narration and animation, a point well proven in his turn as president. Tasked with keeping earth from imminent destruction, David gives the president a no-nonsense energy that helps fuel the race against time to construct the perfect song for the competition. When Rick comes up with “Get Schwifty,” a horrified general questions the song’s meaning. “It’s our world’s best effort, that’s what,” the president curtly replies.

Since Oliver appeared in Harmon’s Community, it makes sense that he would be tapped to voice someone at some point. That opportunity arose in the show’s third episode, “Anatomy Park,” where Rick and his partner Dr. Xenon Bloom build an amusement park inside of a homeless man to form an updated take on Jurassic Park. As the straight-talking doctor who’s trying to keep things going despite the mounting problems (like gonorrhea) arising around his team, Oliver lends Bloom a snarky British attitude that works well for the episode.

Rick’s love life comes into play a few times throughout the series, but never as overtly as in “Auto Erotic Assimilation,” where he encounters his former lover Unity. Needless to say, Unity isn’t like most lovers because she’s an entity who can inhabit multiple beings at the same time. Voiced by Hendricks, who cleverly plays into stereotypes of level-headed women throwing their accomplishments out the window to chase after the bad boy—in this case, Rick—Unity conveys a sweet thoughtfulness that’s no match for Rick’s charm.

Rick finally meets his match—one of his own creation—in “The Ricks Must Be Crazy.” After creating a universe to help power his spaceship, Rick travels to visit it and meets one of their lead scientists, Zeep Xanflorp. Zeep has also created his own universe, much to Rick’s dismay. Like Rick, Zeep is a genius, but that doesn’t mean his social skills are up to par with his intellect, a problem that only furthers the animosity between the two scientists. Known for his ability to play cocky and arrogant, Colbert serves as an ideal voice for Zeep, who keeps pace with Rick at every turn.

In the best use of a guest star, Clement plays a gaseous being that Rick dubs “Fart” in “Mortynight Run.” Appreciating the nomenclature, the being appropriates the name without a whiff of irony. Clement already did a pretty spot-on David Bowie impersonation thanks to his musical comedy in Flight of the Conchords, but here it resurfaces in far more trippy ways. Fart sings songs to Morty that reveal the wonders of the universe, which naturally involve death and destruction. The fact that it’s coming from an extraterrestrial fart notwithstanding, Clement’s voice seems built for the part.

Amanda Wicks is a New Orleans-based freelance writer specializing in comedy and music. Follow her on Twitter @aawicks.