There’s nothing quite like that moment when you’re just relaxing and watching your favourite TV show when, suddenly, your whole perception of reality is challenged by that rarest of things: the crossover episode.

Despite their differences, sometimes TV shows can come together to form one mega-episode, much to our amusement and, occasionally, bafflement. Here are our picks of the most surprising TV crossovers.

20. The Office UK/The Office US

Both The Office UK and The Office US, which respectively began in 2001 and 2005, are the brainchild of funnyman Ricky Gervais. It’s hardly surprising, then, that we would see Gervais’ David Brent pop up in an episode of The Office US in a chance meeting with Steve Carell’s Michael Scott.

Seeing the two characters together somewhat boggles the mind, and Brent’s nasally London tones just do not seem to gel with Scott’s American drawl. The pair meet when Brent applies for Scott’s job and flies out to the Scranton, Pennsylvania branch of Dunder Mifflin for an interview.

19. Roseanne/Absolutely Fabulous

1996’s ninth season of Roseanne radically reworked the sitcom’s set-up by having the working-class Connor family become super-rich from a lottery win. Then, in an episode entitled Satan, Darling, the cast of the British show Absolutely Fabulous showed up. Joanna Lumley’s Patsy and Jennifer Saunders’ Eddie meet (and get drunk with) the newly rich Roseanne on a trip to New York.

Of course, as Roseanne fans will also recall, this episode (directed by Barr, who also co-wrote it with Saunders) was, along with the entirety of season nine, just a dream – and was completely disregarded when the show returned in 2018.

18. The Simpsons/24

Considering both The Simpsons and 24 are Fox shows, it seems only logical that they might one day cross paths. Well, ‘logical’ except for the fact that The Simpsons is a cartoon and 24 is not, and that the fusion of these two worlds makes for a crossover that’s utterly bizarre. Kiefer Sutherland voiced 24’s counter-terrorist hero Jack Bauer in a 2007 episode of The Simpsons, entitled – appropriately enough – 24 Minutes.

This wasn’t the only time characters from a live-action Fox show popped up in The Simpsons; for one, an earlier Simpsons episode features Mulder and Scully of The X-Files (who’ll come up again later).

17. Friends/Mad About You

Fans of 90s sitcoms might have gauged that Friends and Mad About You exist within the same version of New York. The clear link between the two is, of course, Lisa Kudrow, who plays Phoebe in Friends and Phoebe’s twin sister Ursula in both Mad About You and Friends. TV network NBC made a point of exploiting this Kudrow link with a crossover episode in 1994.

In the Friends episode The One with Two Parts, there’s a guest appearance from Mad About You’s Jamie (Helen Hunt) and Fran (Leila Kenzle), with Jamie mistaking Phoebe for Ursula on her visit to Central Perk. This wasn’t the only time Friends crossed over with another 90s sitcom – but we’ll have more on that later…

16. Sabrina the Teenage Witch/Boy Meets World

The 90s teen sitcoms Sabrina the Teenage Witch and Boy Meets World had not one, but two crossovers. The first came in a Halloween episode of Boy Meets World, The Witches of Pennbrook, in which Melissa Joan Hart’s Sabrina makes a quick cameo as the date of Eric (Will Friedle).

These two worlds collided a second time in another Boy Meets World episode entitled No Guts, No Cory, which saw Sabrina’s talking cat Salem send the characters back in time to World War II.

15. The Simpsons/Family Guy

The Simpsons/Family Guy crossover was the animation super-episode that cartoon comedy fans had been waiting for. The shows always had a lot in common, of course: they both revolve around a family with three kids, slightly dysfunctional parents and a dog (although only one of said dogs can speak). Their worlds finally came together on a specially extended 2014 Family Guy episode entitled The Simpsons Guy.

The whole core ensemble of The Simpsons joined the cast of Seth MacFarlane’s show for that episode – and just to make things that bit more ‘meta’ it also features cameos from two other cartoon dads: Bob from Bob’s Burgers, and Fred Flintstone.

14. Full House/Family Matters

Running from 1987 to 1995, Full House was one of the most popular sitcoms of its time – and it once crossed over with another of the era’s best-loved sitcoms, Family Matters. The 1991 Full House episode Stephanie Gets Framed sees Jodie Sweetin’s Stephanie learn she has to wear glasses, which leaves her distraught.

Luckily, Steve Urkel, the bespectacled star of Family Matters, is there to reassure her, appearing as the visiting cousin of a family friend. Family Matters ran from 1989 to 1998 on ABC, then CBS – but unlike Full House (which was latterly brought back as Fuller House), there’s been no revival just yet.

13. The Jeffersons/The Fresh Prince of Bel-Air

Two of our favourite TV families crossed paths in an episode of The Fresh Prince of Bel-Air entitled Will Is from Mars. In the episode, Will (Will Smith) attends relationship counselling with his new fiance, where he meets the Jeffersons, who are also there for a session.

Nor did it end there: in the Fresh Prince of Bel-Air’s finale, the Jeffersons returned as potential buyers for the Banks’ home. We also see some more familiar faces in that final episode, in the form of Mr Drummond and Arnold from Diff’rent Strokes, who are also considering the purchase.

12. Power Rangers in Space/Teenage Mutant Ninja Turtles

The Power Rangers and the Teenage Mutant Ninja Turtles were the two favourite super-teams of every kid back in the 90s – but even so, we never expected to see them team up. However, this happened in the sixth Power Rangers series, Power Rangers in Space, which crossed over with largely forgotten live action series Ninja Turtles: The Next Mutation.

In the episode Shell Shocked, the evil Astronema brainwashes the turtles into working for her, and tricks the Rangers into allowing them aboard their ship. Luckily, an electrical storm reverses the mind control, and the two groups are free to enjoy each other’s company in space.

11. The Mask/Ace Ventura

Aside from both being animated TV shows adapted from movies, The Mask and Ace Ventura have another thing in common: Jim Carrey. OK, so Carrey doesn’t actually feature in either series, but he was in the original movie versions, which must surely count for something.

The two came together in a very special double crossover episode. First, Ace Ventura entered the world of The Mask in a 1997 episode entitled The Aceman Cometh; then, The Mask returned the favour by popping up in an Ace Ventura: Pet Detective episode entitled Have Mask, Will Travel.

10. The X-Files/Cops

As already mentioned, reality-bending detective series The X-Files was one among a number of popular TV shows to have crossed over with The Simpsons. However, you might not be aware that the mysterious adventures of David Duchovny’s Mulder and Gillian Anderson’s Scully also crossed over with another, even more unlikely TV hit.

Season seven of The X-Files boasts an episode entitled X-Cops, which sees our heroic FBI agents joined on duty by a camera crew from reality TV series Cops. As bizarre as this sounds, the episode is often held up as one of the very best ones The X-Files ever did.

9. Archer/Bob’s Burgers

Fans of contemporary adult-oriented animated TV shows will doubtless be familiar with the vocal stylings of H. Jon Benjamin, who not only voices the title character of Bob’s Burgers, but also that of spy spoof series Archer. In the opening episode of Archer’s fourth season, those two very different worlds are brought together in a suitably idiosyncratic manner.

The Archer episode Fugues and Riffs posits that secret agent Sterling Archer has completely lost his memory, and in the interim has gotten married to single mother Linda and started working in their family seafront burger restaurant – but things become complicated when KGB assassins show up.

8. ALF/Gilligan’s Island

Ithere was ever a suitable show for an utterly nonsensical crossover with another goofy TV favourite, it was 80s sci-fi sitcom ALF. Even so, few could have anticipated ALF meeting the cast of Gilligan’s Island – not least because Gilligan’s Island had been cancelled for 20 years at the time.

The Gilligan’s Island ensemble popped up in 1987 ALF episode Somewhere Over the Rerun, in which our hirsute extra-terrestrial visitor becomes obsessed with watching Gilligan’s Island, and somehow finds himself transported into the show.

7. CSI: Crime Scene Investigation/Without a Trace

When it comes to crossover episodes, the popular CSI franchise had no shortage of them across its four incarnations (the original CSI: Crime Scene Investigation plus spin-offs CSI: Miami, CSI: New York and CSI: Cyber). Still, forgetting for the moment crossovers between shows with an already-established link, let’s take a look at the time the original CSI crossed over with rival crime drama Without a Trace.

CSI was on its eighth season and Without a Trace on its seventh when the shows crossed over with a two-part storyline in November 2007, starting with CSI episode Who and What and completed in Without a Trace episode Where and Why, broadcast that same evening with almost 22 million Americans tuning in to watch both episodes back-to-back.

6. Bones/Sleepy Hollow

Bridging the worlds of two largely grounded crime shows like CSI and Without a Trace is logical enough; but crossing over one that’s based in reality and another that’s distinctly supernatural is something rather different. Nonetheless, this is what happened when Bones and Sleepy Hollow decided to crossover just in time for Halloween 2015.

The story began with the Bones season 11 episode The Resurrection in the Remains, then was then wrapped up in the Sleepy Hollow episode Dead Men Tell No Tales (part of that show’s third season).

5. Caroline in the City/Friends

90s sitcom Caroline in the City starred Lea Thompson as cartoonist Caroline Duffy, and the ‘city’ of the title was New York. It was only fitting that Caroline might cross paths with the characters of certain other NY-based sitcoms of the time – so November 1995 episode Caroline and the Folks featured a cameo appearance from Matthew Perry in his Friends role of Chandler Bing.

Thompson’s Caroline returned the favour, appearing in the Friends episode The One with the Baby on the Bus, which was broadcast that very same evening. Another Caroline in the City episode had a cameo from David Hyde Pierce’s Niles and Jane Leeves’ Daphne of Frasier.

4. Supernatural/Scooby-Doo

In horror series Supernatural’s 2018 episode Scoobynatural, the usually live-action paranormal investigators unexpectedly found themselves in animated form, joining forces with another TV team famed for battling the spooky: Mystery Inc., of the long-running Scooby-Doo franchise.

The episode featured guest appearances from the voice actors who’ve worked on all the most recent TV incarnations of Scooby-Doo: Matthew Lillard (Shaggy), Grey Griffin (Daphne), Kate Micucci (Velma), and Frank Welker (Fred and Scooby).

3. Brooklyn Nine-Nine/New Girl

Modern sitcoms Brooklyn Nine-Nine and New Girl did a crossover of their own in 2016. First off, Zooey Deschanel’s Jess of New Girl popped up in Brooklyn Nine-Nine as the driver of a car commandeered by Andy Samberg’s Detective Jake Peralta. This was an unlikely meeting, as New Girl is set on the other side of America in Los Angeles.

Later, the Nine-Nine team had a larger role in a subsequent episode of New Girl which sees Jess’s LA friends fly out to Brooklyn to join her, and where much interaction with local law enforcement ensues.

2. Batman/The Green Hornet

Back in the swinging 60s, Batman and Robin crossed paths with The Green Hornet and Kato on a number of occasions. They first met in 1966 Batman episode The Spell of Tut, followed by Batman two-parter A Piece of the Action/Batman’s Satisfaction, in which the superhero duos do battle both against and alongside one another.

Sadly this wasn’t enough to save The Green Hornet at the time, as the show was cancelled after only one season; but thanks to both the Batman connection and the presence of Bruce Lee, the show has long since attained cult status.

1. Magnum, PI/Murder, She Wrote

In November 1986, the seventh season of Magnum, PI featured an episode entitled The Novel Connection, in which Thomas Magnum’s case sees him cross paths with everyone’s favourite mystery writer and amateur sleuth, Jessica Fletcher.

The events of that episode see Magnum accused of murder – and Fletcher seeks to clear the PI’s name in the following Murder, She Wrote season three episode, entitled Magnum on Ice.