TV Cartoons That Exist In The Same Universe

While the characters in The Simpsons and Adventure Time never actually interacted with each other on-screen, the latter did crossover briefly with Futurama. And since The Simpsons and Futurama did crossover as well, it is reasonable to assume The Simpsons and Adventure Time also exist in the same world together. 

It is a well-known fact that The Flintstones and The Jetsons - two of the most popular animated series of all time - both exist in the same fictional universe. This was revealed through multiple crossover episodes over the years.

As one Redditor wisely surmises, The Jetsons and The Grim Adventures of Billy and Mandy must share the same world as well. This is, of course, based solely on the fact that Fred Flintstone once made a crossover appearance in Grim Adventures.

So, if The Flintstones exist in the same world as Billy and Mandy, then The Jetsons must also. If only we could have seen a crossover between those three shows.

Fans of Rick and Morty and Gravity Falls spent years trying to get some official confirmation that the shows exist in the same universe – if not an actual crossover episode. Unfortunately, despite the creators of both shows packing in loads of references to the other over the years, neither a confirmation nor a crossover episode ever materialized. 

But if there's one piece of evidence that fans always point to as proof that the two series exist within the same world, it's this: There is a moment during the Falls's episode, "Society of the Blind Eye," when Grunkle Stan's notepad, pen, and drink mug are all sucked into a multi-dimensional vortex. During "Close Encounter of the Rick Kind," you can very quickly see all three of those items appear in a portal in Rick and Morty's world.

The proof of this connection is available via an episode of Samurai Jack in which Jack and company walk by a tattered billboard – the exact same tattered billboard seen previously in an episode of The Powerpuff Girls.

This leads some to theorize that Samurai Jack takes place in the future, possibly centuries after Townsville and all of its inhabitants have been destroyed as a part of Aku's apocalyptic plans.

During its run on the Disney Channel, Phineas and Ferb crossed over with multiple other shows that also lived under the Disney banner. However, if there was one major title that fans always wanted to (but never got to see) Phineas and Ferb cross over with, it was Gravity Falls. Although, that may not have stopped the Gravity Falls writers from subtly acknowledging that the two shows take place in the same universe.

As one observant Redditor noted, there's a very specific Phineas and Ferb reference placed early on in the Gravity Falls's first season, when Dipper quotes Phineas's key catchphrase and says, "Yes, yes I am."

Despite its subtlety, it's no doubt a clever nod to the Phineas character.

Dexter's Laboratory and The Powerpuff Girls are two of the most iconic and beloved Cartoon Network shows of all time. Not only are the programs immensely popular, but both have proven to be equally influential in shaping the modern day view of what the network is.

As has been noted many times before, there were multiple cameo appearances by Dexter made in The Powerpuff Girls episodes throughout the years, including one time in which the boy-genius was seen sleeping in the same kindergarten class as the girls.

Like many of the other connections on this list, however, a shared universe was never officially acknowledged by either creator.