This is far from the first time that multiple TV shows have crossed over, however, even if past team up events haven’t come packing quite so many superpowers. Sitcoms, animated series, and even police procedurals have enjoyed shared universe adventures. Some, like the Arrowverse, are special events in worlds that viewers already knew to be connected, but others jumped into whole new areas for one-off episodes… and we’ve got a run down of the best ones so far.

Here are the 15 Best TV Crossover Episodes Of All Time. 

15. The Arrowverse

There have already been multiple crossovers and spin-offs since Oliver Queen (Stephen Amell) first burst onto the small screen with his solo series in 2012. First, Barry Allen (Grant Gustin) found his way to Central City before an entire team of characters spun-off from the combined might of Arrow and The Flash to become the Legends of Tomorrow.

The three shows have already had one major crossover event, which saw the heroes battling Vandal Savage (Casper Crump), as well as multiple minor crossovers where various individual characters would jump shows for an episode or two. We even saw Arrow crossover with a cancelled series, when Constantine (Matt Ryan) was welcomed onto the show to the joy of fans who were heartbroken when his solo adventures were canned by NBC. The DC crew also managed to jump networks a second time when the Flash ran his way into Supergirl’s alternate universe during Supergirl season one – before the show officially became part of the CW family.

There’s no denying it, folks: the Arrowverse is the one true king of the crossover.

14. Buffy The Vampire Slayer/Angel

Angel began life as a spin-off from Joss Whedon’s Buffy Summers (Sarah Michelle Gellar), and their tumultuous romance was a huge part of the early seasons of Buffy. Their relationship ended when Angel decided that Buffy needed a chance at a normal life and future, leaving Sunnydale for LA to start Angel Investigations. Although that was the end of a relationship for the two, they did occasionally travel between Sunnydale and the city of angels to help each other out.

During season four of Buffy, Angel makes some surreptitious visits back to Sunnydale, before Buffy heads to LA to confront him about it in "I Will You". Later, in Buffy season five, Angel returns again for Buffy’s mother’s funeral; these two just never seem to see each other unless it’s to break the viewer’s heart!

13. The Simpsons/Family Guy

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Given the overwhelming resemblance between these two long-running shows, it’s no surprise that the pair eventually crossed over in 2014 with "The Simpsons Guy". This one-off episode revolved around the shows’ similarities with a Duff vs Pawtucket Patriot copyright lawsuit that saw similar characters from both shows squaring off in the courtroom. Chock full of references to iconic jokes from both shows (Peter and Homer get into a chicken-fight, Stewie writes lines on the blackboard), the crossover also explored some of the ways that the shows differ (especially the more graphic nature of Family Guy). Although the episode wasn’t intended to create a combined universe, the door has been left open for another Griffin/Simpson meet up down the line, if fans want it.

12. CSI/CSI: New York/CSI: Miami/Without A Trace/Cold Case

The hugely popular crime drama CSI: Crime Scene Investigation has spawned multiple spin-off series since it first aired in the year 2000, some of which gained their own success (CSI: New York and CSI: Miami), and some of which didn’t quite make it on their own (CSI: Cyber). The three main CSI shows have crossed over multiple times in multi-episode specials that usually involve tracking a killer across state lines. Detectives have wandered from one show to another eight times over the fifteen years that CSI was on the air, with one massive three-part episode titled "CSI: Trilogy" that linked CSI, CSI: New York and CSI: Miami (before the days of CSI: Cyber).

The franchise has also connected with two other crime procedurals as well. Cold Case’s Scotty Valens (Danny Pino) visited the New York crime lab for the 2007 episode "Cold Reveal" as a one-off guest star. CSI also managed a full two-episode crossover with Without A Trace in 2007, making that the year of the crime procedural shared universe!

11. Law & Order: SVU/Everything

Another long-running police procedural,  Law & Order franchise, which has seen multiple crossover episodes over the years. Characters from Law & Order have ed forces with those in Law & Order: SVU, Law & Order: Criminal Intent, Law & Order: LA, Homicide: Life on the Street, and so on. Most of these aren’t major crossover events, however – this is a massive universe where all the characters work in law enforcement in the same country, and character swapping, while exciting for fans, isn’t usually treated as a huge deal.

However, there is one Law & Order character in particular who deserves a special mention for the sheer number of crossovers he has been in, within and outside of the Law & Order franchise: Detective John Munch (Richard Belzer). Created for Homicide: Life On The Street, Munch moved from there to Law & Order: SVU, but has also appeared in a huge range of other shows, including The Unbreakable Kimmy Schmidt.

10. Mork & Mindy/Happy Days/Laverne and Shirley

Another massive shared universe that almost rivals that of Law & Order, the Happy Days franchise inspired several spin-offs, with two actually finding their own success (Laverne & Shirley and Mork & Mindy). Although most of the Happy Days gang stayed put within their own show (or wandered away to star in their own spin-off adventures), Fonzie (Henry Winkler) spent a fair bit of time appearing in multiple series within the franchise.

One of the best crossover episodes, however, is the pilot episode of Mork & Mindy, where Mork (Robin Williams) tells the story of his first visit to Earth, when he met the Fonz and went on a date with Laverne (Penny Marshall). It was a fantastic way to link the three shows without needing them to awkwardly connect in the present day, and although the Fonz made many more appearances on Laverne & Shirley, this three-part crossover is a little bit special.

9. Full House/Family Matters

Fuller House, but it was the original series that included this particularly memorable crossover episode. In "Stephanie Gets Framed", Stephanie (Jodie Sweetin) is heartbroken to discover that she is going to have to get glasses. Luckily, she gets a visit from one of the most beloved four-eyed characters in sitcom land: Steve Urkel (Jaleel White).

The star of Family Matters appears as the visiting cousin of a friend in a fairly typical crossover connection, and he helps Stephanie come to with her new eyewear. It’s the only episode of the two series that cross over (we imagine DJ’s friend’s cousin wore out his welcome on the first visit!), which is something of a shame, as we would have loved to see Urkel reappear. Perhaps he could pop up as a guest star in a future episode of Fuller House, and let us all see what an adult Urkel is up to.

8. Friends/Mad About You/Seinfeld

Three of the biggest sitcoms of the ‘90s all took place in New York, but not many fans realize (or ) that they actually all co-exist within the same version of the Big Apple. The three have connected more than once, although there have also been some inconsistencies between them, leading eagle-eyed fans to question their connections.

Lisa Kudrow is the obvious connection between Seinfeld, in an episode where Kramer (Michael Richards) sublets an apartment from Paul (Paul Reiser). It’s a much smaller connection than the one between Friends and Mad About You, but it’s enough to convince us that all three shows exist in one world.

As for the time that Seinfeld characters watched an episode of Mad About You, or Courtney Cox’s appearance on Seinfeld as a totally different character? We’re just chalking those ones up to ‘90s sitcom logic.

7. Batman/The Green Hornet

Long before Arrow and its expansive universe brought the Emerald Archer to the small screen, Batman was the superhero du jour for TV viewers. And he also had a superhero crossover episode -- with the Green Hornet.

Despite the fact that the Green Hornet (Van Williams) wasn’t a DC character at the time (although he is now licensed to DC), he and his trusty sidekick Kato (Bruce Lee) headed to Gotham City in 1967 to try and take down a counterfeiting operation. They start off being perceived as a threat to Adam West’s gloriously campy Batman, before everyone realizes that they are on the same side, and we get some fantastic retro team up action. Sadly, this wasn’t enough to boost the popularity of The Green Hornet, which was cancelled after only a single twenty-six episode season.

Although the character hasn’t had much on-screen success (the 2011 movie was also a disappointment), we'd love to see another Hornet resurrection and a crossover into the Arrowverse. We'll settle for Gavin Conner's cinematic reboot of the franchise, though.

6. Sabrina The Teenage Witch/Boy Meets World

These two ‘90s young adult sitcoms had two crossovers, and both of them were definitely on the oddball side (which isn’t too surprising, given the magical nature of Sabrina The Teenage Witch).

In a Halloween episode of Boy Meets World ("The Witches of Pennrbook"), Jack (Matthew Lawrence) and Eric (Will Friedle) nearly come to blows over Jack's new girlfriend Millie (Candace Canmeron) – who turns out to be a witch! She’s definitely the bad kind, unlike Sabrina (Melissa Joan Hart), who appears at the end of the episode as a date for Eric in a brief cameo.

Sabrina’s world has a slightly bigger impact in "No Guts, No Cory", a Boy Meets World episode where the Spellman’s talking cat, Salem (Nick Bakay), sends the characters back in time to World War II. There’s no real reason for this particular spell (or crossover in general), but it’s certainly a fun experience for the viewers, and it ends with a sweet moment as Cory (Ben Savage) gives Topanga (Danielle Fishel) a ring from a cracker jack box.