The concept behind crossovers did not originate with the Marvel Cinematic Universe. Comics have been staging similar events for decades, and the same can be said for film and television. Now, in all fairness, The Avengers deserves credit for following through on an ambitious gameplan that could have easily backfired; nevertheless, studios have put together far weirder crossovers than a pack of superheroes teaming up to fight Thanos.

Anyone with a Deviant Art account should be privy to an overwhelming amount of fan-created relationships featuring members from entirely unrelated properties. Have you ever dreamed of seeing Frozen's Elsa partner up with Rise of the Guardians' Jack Frost? A quick google search should quickly scratch that itch! These communities provide a look into an alternate reality which cannot be explored by the actual source materials. Disney and DreamWorks are rivals, therefore, that How to Train Your Dragon and Tangled crossover must remain an unattainable dream.

Whether requested or not, viewers have been treated to a wild array of peculiar crossovers. While these type of events are not quite as common as they were during the 1980s, most years tend to include a handful of surprise guest appearances. Are they a match made in heaven? Or, should these characters have remained in their own cartoons? Unsurprisingly, fans have been subjected to a decent amount of both outcomes.

Here are the 15 best crossovers in cartoon history (and the 15 worst)!

30 Best: The Lego Movie

Via medium.com

Sitting with an impeccable 96% on Rotten Tomatoes, The Lego Movie was far better than anyone could have envisioned. Boasting gorgeous 3D animation and a surprisingly heartfelt third-act, this project could have easily turned out to be a mess.

The Emoji Movie showcases the mistakes that can be made with this type of flick, but The Lego Movie comes across as a sincere celebration of the popular building blocks. If nothing else, we got to see Gandalf and Batman share a scene!

29 Worst: Mickey's 60th Birthday

Via disney.wikia.com

Released during the same year as Who Framed Roger RabbitMickey's 60th Birthday celebrated the mouse's anniversary. Interjecting animated figures into live-action backdrops, Mickey leads viewers on an excursion through Disney's studio. While it would be unreasonable to expect a television special to match a feature film's production, Mickey's 60th Birthday falls short in nearly every department.

Simply put, NBC's segment is unpleasant and boring!

Various toons from Mickey's past make an appearance, but Mickey's 60th Birthday seldom succeeds in convincingly blending the live-action with the animation. Green screen has scarcely looked so obvious.

28 Best: Who Framed Roger Rabbit

Via ReggiesTake.com

Based on Gary K. Wolf's Who Censored Roger Rabit?, Robert Zemeckis' adaptation pays loving tribute to classic cartoons, while simultaneously unraveling a fascinating neo-noir mystery. Set in a universe where cartoons exist alongside humans, Who Framed Roger Rabbit is a technical marvel and has aged splendidly. Even though the main plot revolves around original cartoon characters, principally Roger and Jessica Rabbit, the film is laced with high profile cameos.

As long as neither studio felt short-changed, Warner Bros. and Disney agreed to allow their iconic personas to briefly share the screen. In one of many memorable scenes, Donald and Daffy battle it out to see who is the craziest duck in the game!

27 Worst: The Simpsons & Family Guy

Via Vulture.com

Launching Family Guy's 13th season, The Simpsons Guy barely makes the grade as a mediocre entry in Seth MacFarlane's franchise. The Simpsons has seen better days, but the legendary animated sitcom tends to approach situations with a lighter touch than Family Guy.

Rather than elevating MacFarlane's style of shock humor, The Simpsons seemed happy to be dragged down to Family Guy's level.

Deprived of even the tiniest hint of wit or subtlety, The Simpsons Guy incorporates the worst elements of both properties.

26 Best: DCaU

Via ew.com

Putting aside Wonder Woman and parts of Man of Steel, the DC Extended Universe has failed to replicate Marvel's success. Haphazardly throwing multiple characters together in hopes of something sticking, DC could use a bit of a patience.

Frustratingly, the brand has experience creating a fantastic shared timeline, as the DC Animated Universe spanned multiple series, films, and comic books! Inaugurated with Batman: The Animated Series and lasting longer than a decade, the project culminated with the brilliant Justice League Unlimited. Combining characters from across several DC properties, this cartoon is the ultimate crossover!

25 Worst: Cartoon All-Stars To The Rescue

Via vice.com

An after-school special masquerading as a crossover, Cartoon All-Stars To The Rescue is a PTA advising children to resist injecting anything illegal into their systems. A young teenager with a monkey on his back, Michael steals his sister's piggy bank to feed the beast; luckily, various cartoon characters show up to take the kid on an educational journey about the dangers of Mary Jane.

Focusing on a something that has been legalized in certain states, Cartoon All-Stars To The Rescue is a laughable attempt to scare children away from certain substances.

24 Best: The Jetsons Meet The Flintstones

Via mubi.com

Desperately striving to revive interest in its properties, Hanna-Barbera greenlit 10 made-for-television animated films. Broadcast in 1987, The Jetsons Meet the Flintstones is arguably the strongest movie out of the bunch. Coinciding with a series revival for the former, the plot essentially boils down to a role reversal.

Stuck in the Stone Age, George Jetson ends up working for Mr. Slate; conversely, the Flintstones take a trip to the future. As far as cheap crossovers go, The Jetsons Meet the Flintstones fares better than most. Admittedly, this special is solely for fans of both series, but the characters stay true to themselves.

23 Worst: Steven Universe & Grandpa Uncle

Via imdb.com

While both series formed part of Cartoon Network's line-up, Steven Universe and Uncle Grandpa strike inherently different tones. The former tends to aim for an overarching storyline and a sense of continuity, while the latter is more of an absurdity comedy with an incredibly annoying protagonist.

Even next to some other entries in this article, Say Uncle is weird.

Unable to recall his shield, Steven accidentally summons Uncle Grandpa, who decides the only way to fix this issue is to attack the boy with every available weapon. Far too pointless to pass as an episode of Steven Universe and lacking Uncle Grandpa's insane visuals, Say Uncle is a crossover for nobody.

22 Best: Laff-A-Lympics

Via fredthebluraydog.com

Once upon a time, Hanna-Barbera executives conducted a meeting to discuss ideas capable of reviving interest in their cartoons. Could a new Scooby-Doo series do the trick? How about revisiting Wacky Racers? Out of nowhere, one brave soul stood up and shouted Laff-A-Lympics!

As implied by the title, this was an Olympics-themed cartoon starring dozens of Hanna-Barbera's beloved icons. Divided into three separate teams; the Scooby Doobies, Yogi Yahooeys, and Really Rottens competed across numerous sports to crown a winner. Pushing past the silly premise, Laff-A-Lympics was a unique cartoon that should have generated more than merely 24 episodes.

21 Worst: Ultimate Spider-Man & Jessie

Via marvel.wikia.com

Technically, this crossover consisted of only one cartoon, but Jessie is about as realistic as an animated series. Love or hate it, Ultimate Spider-Man lives in a completely separate realm to Disney's sitcoms. Frankly, this crossover should not exist, and this Halloween episode offered little incentive to alter this belief.

How did this union come to pass?

Well, Jessie and Ultimate Spider-Man both take place in New York. That's it. While Wizards of Waverly Place's magical element lends itself to such a crossover, Jessie is grounded in some semblance of reality. These children do not belong on the same screen as Peter Parker.

20 Best: Lupin The 3rd Vs. Detective Conan: The Movie

Via TheMovieList.net

As a stand-alone feature film, Lupin the 3rd vs. Detective Conan: The Movie can be rather hit and miss; nevertheless, fans of both franchises should enjoy this remarkable crossover.

Pitting the world's greatest thief against the genius detective, this 2013 crossover boasts some solid animation, an avalanche of in-jokes, and a serviceable storyline. While nowhere near as good as The Castle of Cagliostro or Detective Conan: Jolly Roger in the Deep Azure, this project is a fun ride starring two of anime's most iconic protagonists.

19 Worst: Ben 10 & The Secret Saturdays

Via aminoapps.com

Lasting for three seasons and airing its finale in 2010, The Secret Saturdays sprinkled numerous references hinting at a shared universe with Ben 10. Unfortunately, a crossover would not happen until Ben 10: Omniverse, a reboot series created far after the franchise's glory days.

On its own, T.G.I.S. is a pretty decent episode, but The Secret Saturdays lacks the name recognition to share equal billing with Ben 10. Consequently, the Saturdays feel more like children meeting their ideal during a Make-A-Wish event than heroes fighting on level footing with Ben Tennyson.

18 Best: Johnny Bravo & Scooby-Doo

Via scoobydoo.wikia.com

Bravo Dooby-Doo is hilarious. Over the years, Scooby-Doo has been subjected to thousands of crossovers, with some being better than others. In the same vein that ScoobyNatural injects Hanna-Barbera's license into Supernatural's universe, Scooby-Doo's crossovers work best when the meddling teenagers are the guests rather than the hosts.

Broken down on the side of the road, Johnny Bravo is picked up by the Scooby gang and tags along during a subsequent mystery. Subverting many tropes associated with Hanna-Barbera's classic cartoon, Bravo Dooby-Doo might look like Scooby-Doo, but it has Johnny Bravo's sense of humor.

17 Worst: Daffy Duck And Porky Pig Meet The Groovie Goolies

Via dailymotion.com

Surprisingly, this forgotten movie marks the only time Warner Bros. permitted Filmation to use Looney Tunes characters. Producing hundreds of cartoons for CBS, ABC, and NBC; Filmation was responsible for He-Man and the Masters of the Universe and various comic book adaptations. Released in 1972, Daffy Duck and Porky Pig Meet the Groovie Goolies pivots around a sinister ghoul who yearns to destroy any film starring Daffy Duck.

Due to never acquiring a home video release, this made-for-TV movie can be a challenge to track down, and the effort is not justified. Hollywood has birthed worse crossovers, but Daffy Duck and Porky Pig Meet the Groovie Goolies is inconsequential.

16 Best: Phineas And Ferb: Mission Marvel

Via phineasandferb.wikia.com

Accomplishing what Loki failed to do across three movies, Dr. Doofenschmirtz defeats Marvel's superfriends by draining their powers. Once news spreads about the ineffective Avengers, a myriad of supervillains attack the defenseless Danville, prompting Phineas and Ferb to work tirelessly in order to reverse Doofenshmirtz's influence.

Phineas and Ferb: Mission Marvel's premise is somewhat contrived, but this crossover is a fun throwback to the more lighthearted comics of yesteryear. Packed with fantastic in-jokes and witty one-liners, Mission Marvel should be a blast for Phineas and Ferb or Marvel fans.

15 Worst: The Cleveland Show & The Simpsons

Via cleveland.fandom.com

The self-proclaimed worst cameo ever, The Simpsons' Comic Book Guy briefly joined Cleveland Brown on screen during the episode Hot Cocoa Bang Bang. The creator of the terrible Waderman graphic novel, Cleveland sets up a booth at Comic-Con to connect with his (non-existent) reader base.

Harmless and hardly worse than The Cleveland Show's usual jokes, Comic Book Guy's cameo suited the character and served as a neat Easter Egg for viewers. However, it would just feel wrong to place this under the "best" section.

14 Best: Spider-Man & The X-Men

Via archive.4plebs.org

A staple of the animated scene during the '90s, Spider-Man: The Animated Series and X-Men: The Animated Series combined their respective prowess to birth an awesome two-part crossover. Worried he might be mutating into a monster, Peter reaches out to Charles Xavier for advice; unfortunately, this leads to a corrupt corporation capturing Beast and Spider-Man shouldering the blame for it.

Despite airing on Fox Kids and falling under Marvel's umbrella, these cartoons were produced by different companies, which complicated a possible crossover. Ultimately, things did work out, allowing for Spider-Man and Wolverine to share the screen.

13 Worst: Rugrats Go Wild

Via netflixmovies.com

The final entry in a trilogy starring Nickelodeon's babies, Rugrats Go Wild is the product of a tired franchise devoid of any lingering traces of originality. Following the enjoyable Rugrats in Paris: The Movie, this 2003 sequel tried to cover the cracks by injecting The Wild Thornberrys into the adventure.

At the time, both cartoons were past their prime, a fact that is painstakingly evident in Rugrats Go Wild.

Formulaic to the point of tedium, this crossover did little to help reinvigorate either property. In fact, Rugrats Go Wild signaled the end of the line for Nickelodeon's popular shows.

12 Best: Animaniacs (All Of Them!)

Via cancel.tv

Following Hulu's announcement that an Animaniacs reboot is set for a 2020 release, there has never been a more appropriate time to re-watch Steven Spielberg's cartoon. Starring the Warner siblings and a number of other cartoon characters, Animaniacs' humor is reminiscent of early Looney Tunes shorts.

Refusing to shy away from any inappropriate cameos, Animaniacs interjected the likes of Bruce Wayne, Don Corleone, Prince, and Freakazoid into its hijinks-packed sketches. A handful of these cameos were promotional, but the majority took advantage of the crossovers' inherent bizarreness!

11 Worst: Ace Venture & The Mask

Via funnyjunk.com

With this entry, we have something of a conundrum. Based on Jim Carrey's popular comedies, The Mask and Ace Ventura were both subjected to underwhelming animated spin-offs that captured little of the source materials' charms.

Serving as the series finale for The Mask: The Animated Series and bringing to a close Ace Ventura: Pet Detective's second season, this crossover hits about the same level of quality as the rest of the episodes. In other words, these two segments principally consist of cheap animation and an orchestra of fart noises. Unless someone is a huge Carrey fan, there is no point seeking out this crossover.