Arguably the defining cartoon of the 2010s, let's discuss a show that defies categorization, crossing over many ideas and exploring vastly different genres from horror to sci-fi, with an emotional story about family and centering on a goofy and angry grandfather and a well meaning but easily manipulated grandson that gets in all sorts of troubles, many of them caused by teenage hormones and a crush on an older girl. 

That's right, we're talking about the hugely influential "Rick and Morty." Or is it the hugely influential "Gravity Falls?"

These high-concept shows offer riffs on pop culture and a variety of genre-crossing stories that captivated and entertained audiences around the world. But as different as they are, "Rick and Morty" and "Gravity Falls" have some surprising crossover in addition to the similarities mentioned above. Their creators, Justin Roiland and Alex Hirsch, have been friends for years and they took every chance they got to tease audiences and introduce little easter eggs to each other's shows — from supplies being sucked into a portal in "Gravity Falls" ending up in "Rick and Morty," or a Bill Cipher symbol in the background of a "Rick and Morty" episode.

This also means there is some crossover with the casts, with some voice actors portraying characters on both shows. Here are some names you may not know appeared in both "Rick and Morty" and "Gravity Falls."

Alfred Molina

Alfred Molina is one of our most legendary character actors, who made his debut in "Raiders of the Lost Ark" and has since appeared in everything from "Spider-Man" to "The Pink Panther 2." Molina always brings gravitas to every role he plays, whether it's live-action or animation, having lent his voice to shows like "Wizards: Tales of Arcadia," "Harley Quinn," "Robot Chicken," and "The Wild Thornberrys."

Molina visited "Gravity Falls" when he voiced Multi-Bear in the episode "Dipper vs. Manliness." The Multi-Bear is a magical beast with eight heads, including one smart head that can speak. His mortal enemies are the "Manotaurs" that want to kill him just for liking the sweet, sweet sounds of Icelandic pop sensation BABBA, with Multi-Bear's favorite song being "Disco Girl."

When he traveled the multiverse and landed in "Rick and Morty," Molina voiced the mischievous Mr. Lucius Needful, a disguise for the Devil himself. Here he is portrayed as an eccentric man running a vintage antique shop where he sells cursed merchandise in a hipster version of a Faustian bargain, wherein he sells people items that will grant them good things, at terrible costs — like a typewriter that only writes bestselling murder mysteries but causes the stories to happen in real life.

Patton Oswalt

Patton Oswalt has appeared in some hugely popular sitcoms from "The King of Queens," to "Seinfeld," but he is legendary in animation for having a rather prolific career as a voice actor. Though he is perhaps best known for playing Remy in "Ratatouille," Oswalt has appeared in everything from "Bob's Burgers" to "Batman Beyond" and many, many more shows and films.

The actor appeared in the second season episode of "Rick and Morty" titled "Auto Erotic Assimilation" as Beta-Seven, a hivemind and parody of the Borg from "Star Trek." The episode follows Rick getting involved in a toxic romantic relationship with the hivemind Unity that quite literally controls an entire planet. Oswalt plays a jealous ex-boyfriend. 

In a very, very different role, Oswalt voiced Franz, the leader of the Dutchman Lilliputtians that live on the 18th hole at the mini-golf course from the season two episode "The Golf War" from "Gravity Falls." The episode follows Mabel's attempt to humiliate Pacifica by challenging her to a miniature golf competition, which escalates out of control when the strange golf ball-like creatures known as Lilluputtians offered their help.

Nathan Fillion

Nathan Fillion is no stranger to sci-fi and genre in general, having played the leading role of Captain Malcolm "Mal" Reynolds on the cult classic "Firefly" TV show. Even his cop procedural "Castle" had plenty of genre-adjacent episodes, many of which were inspired by the works of Stephen King. As a voice actor, Fillion played Hal Jordan, aka Green Lantern in several DC animated movies, the bully in "Monsters University," Jessi's Dog in "Big Mouth" and more.

Of course, we don't care about that. What matters is that Fillion played Cornvelious Daniel in "Rick and Morty," an agent from the Galactic Federation tasked with gaining the formula for interdimensional travel from Rick Sanchez. In the season 3 premiere, Cornvelious uses a device to travel inside the brain of Rick and gain access to his memories but instead of the formula he gets a taste of Szechuan sauce and becomes obsessed with it.

In "Gravity Falls" he plays Preston Northwest, the father of Mabel's archenemy Pacifica Northwest, the rich girl in town. Preston is the great-grandson of alleged town founder Nathaniel Northwest. Where Pacifica is just a mean girl, Preston is a ruthless, merciless millionaire man who despises anyone of a lower economic class than he is.

John Oliver

John Oliver is responsible for some of the best reporting in a talk show ever made, giving us funny but informative episodes of "Last Week Tonight" every week (while reminding us he is the exact same age as John Cena). Outside of that show, Oliver played one of the best side characters in "Community," Professor Ian Duncan. As a voice actor, Oliver acted in films like "The Smurfs," and played Zazu in the CG remake of "The Lion King."

Oliver appeared in the third ever episode of "Rick and Morty" as the John Hammond knock-off Dr. Xenon Bloom, an amoeba who co-founded Anatomy Park with Rick, a theme park inside the disease-infested body of a homeless man named Ruben. Sadly, when the park inevitably goes out of control and the diseases start killing the guests, Dr. Bloom is killed by E. coli while saving Morty.

Similarly, Oliver appeared in the third ever episode of "Gravity Falls," which is kind of a parody of "Night at the Museum," but with wax figures coming to life. Oliver plays Wax Sherlock Holmes, the leader of the wax figures who fights Dipper, murders Wax Stan, and dies when exposed to the rising sun. 

John DiMaggio

John DiMaggio is a legend of voice acting. An actor who has given us beloved characters in tons of cartoons and video games. His versatile voice has given life to Bender on "Futurama," Jake the Dog on "Adventure Time," The Scotsman on "Samurai Jack," Marcus Fenix in the "Gears of War" video games, and more. 

DiMaggio played the character of Trandor in the "Rick and Morty" episode "The ABCs of Beth," which follows Rick and Beth revisiting her childhood issues on a planet called Froopyland, while Morty and Summer have suspicious about Jerry's girlfriend Kiara. Trandor is Kiara's ex-boyfriend, a mighty warrior from a distant planet who gets mad at Jerry for dating his ex.

In "Gravity Falls," DiMaggio gave life to "Manly" Daniel Corduroy, the manliest lumberjack in all of Oregon. He is the father of Wendy Corduroy, Dipper's crush. When we first meet him, he is teaching his sons how to fish, but rather than use a pole he catches a fish with his bare hands and kills it with a single punch. 

Alex Hirsch

You may know the name Alex Hirsch from earlier in this very article, or such hits as, well, "Gravity Falls." In that show, Hirsch voices fan-favorites Grunkle Stan, the eccentric owner of the Mystery Shack, his employee Soos, and the interdimensional villain Bill Cipher. 

In "Rick and Morty," Hirsch has a cameo as Toby Matthews, a boy that Summer has a crush on; she invites to a party at her house hosted by Tiny Rick. At some point later, the Galactic Federation took over Earth and they loved Toby so much that they cataloged his entire brain and turned his favorite memories into a short film.

Justin Roiland

Justin Roiland is one of the biggest names in TV cartoons, having co-created both "Rick and Morty," and also "Solar Opposites," but Roiland is not just a great writer, he is also a really good voice actor — even if he doesn't have the biggest range. 

In addition to creating "Rick and Morty," Roiland also voices both of its titular characters, Rick Sanchez and Morty Smith. In "Solar Opposites," Roiland voices one of the main characters, Korvo.

But before "Rick and Morty" even premiered, Roiland appeared in the "Gravity Falls" episode "The Time Traveler's Pig," which parodies "The Butterfly Effect" and follows Dipper as he travels back in time to correct a mistake but makes things worse every time. The episode guest stars Roiland as Blendin Blandin, a time traveler from the year 207̃012 who loses his job because of Dipper and Mabel and swears revenge on the twins. He appears several times throughout the show.

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