5 Fan-Favorite TV Shared Universes Analyzed

Mike Delaney
TV Star Trek
TV Star Trek Marvel Arrowverse DC

Last week, The CW pulled off a truly impressive achievement – a four-way crossover between its DC television shows. Heroes from Supergirl, The Flash, Arrow, and DC’s Legends of Tomorrow joined forces in a special four-night event to battle the alien race known as the Dominators. The scale and interconnectedness is a real achievement, but crossovers and shared universes on TV are nothing new.

We’ll take a look at how the Arrowverse does it, revisit some of the shared TV universes that have graced our screens over the years, and gauge their level of connectivity – or lack thereof.

The Arrowverse


Arrow may have been the first show in the Arrowverse, but it is arguably The Flash that is the most influential. The Flash introduced concepts such as Metahumans, time travel, and parallel Earths which allowed both Legends of Tomorrow to become a reality, and to successfully (if not smoothly) integrate Supergirl into the Arrowverse. Barry Allen‘s creation of Flashpoint at the end of Season 2 has had lasting repercussions not only for The Flash, but for Arrow and Legends of Tomorrow as well. It is yet to be seen if Supergirl will be affected in any way, but chances are it will not be – The Flash has already established that Flashpoint is confined to Earth-1.

Arrow is seemingly unaffected by Barry’s actions until the revelation that John Diggle’s daughter, Sara, never existed but was replaced by John Diggle Jr. A grown-up version of John Diggle, Jr featured in an episode of Legends of Tomorrow set in Star City in 2046 where he was a future version of the Green Arrow. Professor Martin Stein also postulates the theory that the time aberrations the Legends have been dealing with in Season 2 have been the result of Flashpoint – and with Eobard Thawne responsible for “correcting” Flashpoint and now on the lose throughout history, it seems connected at the very least.

This kind of impact on related shows is unusual to say the least. Even with the interconnectivity between the shows, there are likely viewers who watch only Supergirl, or Arrow, and do not bother with the others. To have wide reaching consequences for a character like John Diggle to have occurred outside his parent show is a bold choice. Even in interconnected shows like Star Trek, crossovers rarely impact the ongoing nature of the show with everything returning to the status quo next week. The Arrowverse is different. Barry’s secret is out, and everyone has to deal with it. But the upside is that now Supergirl has a method of travel between universes to facilitate faster crossovers.

Star Trek

star-trek TOS cast

Starting in 1966, Star Trek is one of the biggest fictional shared universes. The Original Series has spawned four live-action spin-offs, an animated series, a film series, and now a new in-development television series. The franchise is fifty years old with no signs of stopping. But even this large, venerable series has not really embraced the kind of crossover that the Arrowverse managed. Setting aside the movies with their crossover plots (both the original timeline and the Kelvin timeline), crossovers were generally not embraced by Star Trek, even when more than one series was running concurrently.

On occasion, certain characters crossed over between the shows. Doctor Bashir appears in the first part of the two-part episode Birthright when the ship is docked at Deep Space 9. Geordi La Forge appeared in an episode of Voyager as the future captain of the U.S.S. Challenger. Other recurring characters like Q and Vash also appear across multiple series. Jonathan Frakes holds an impressive achievement by appearing in all four of the spin-off Star Trek series. He plays Commander William Riker in The Next Generation, Voyager, and Enterprise, while portraying Riker’s transport duplicate, Thomas, in Deep Space Nine. However, despite these crossovers, not one of them truly impacted the ongoing plot of any series.

One shining example, though, of Star Trek‘s crossover was the tradition of having a character from a previous series guest star in the spin-off’s pilot episode. DeForest Kelley reprised his role as an aging Admiral Leonard McCoy in a beautiful scene with Data. Patrick Stewart guest-starred as Captain Jean-Luc Picard in Deep Space Nine in scenes opposite Commander Benjamin Sisko. Sisko’s wife had been killed in the Battle of Wolf 359, when a Starfleet force had been massacred by a Borg cube under the command of an assimilated Picard. Voyager featured scenes set on Deep Space Nine where Harry Kim and Tom Paris were almost swindled by Ferengi bartender Quark. When it came to Enterprise, however, there was no previous series to draw an actor from – so they brought in James Cromwell‘s Zefram Cochrane from Star Trek: First Contact.

The Buffyverse


Buffy The Vampire Slayer only had one spin-off show: Angel. The two shows crossed over several times, but after two seasons on the air, Buffy moved to a different network and outright crossovers were actually banned for a time. Despite this, there were several times when Angel directly impacted its parent show’s storylines. The redemption of the rogue Slayer, Faith was started in Angel and completed in Buffy’s final season when the character returned to Sunnydale to help in the fight against the First Evil.

Angel had a further impact on Buffy‘s final episodes. At the end of Season 4, Angel accepts the position of head of evil law form Wolfram & Hart after Lilah Morgan offers him an amulet that will be instrumental in aiding Buffy’s forthcoming battle against the First Evil at the Hellmouth. Angel travels to Sunnydale and gives Buffy the amulet, which is to be worn by “someone ensouled but more than Human.” Angel initially intends to fight alongside Buffy wearing the amulet, but she orders him to prepare a second front in case she fails.

Spike ends up wearing  the amulet, and during the final battle it seemingly kills him but succeeds in destroying the First Evil and their Turok-Han army. Without Angel’s intervention, the outcome of the battle would presumably have been very different. Buffy ended its seven year run on television at that point, but in the opening episode of Angel Season 5, Angel receives the amulet back in the post – which promptly dumps a resurrected (if ghostly for a time) Spike on his doorstep.

Marvel Cinematic Universe

The Defenders

Marvel’s deal with Netflix to produce a series of interconnected shows showcasing Davedevil, Jessica Jones, Luke Cage, and Iron Fist, culminating in a miniseries starring all of them, pretty much guaranteed tight plotting and numerous connections between the series. And fans have not been disappointed. Starting with Daredevil‘s mentions of the Battle of New York (known as The Incident) from The Avengers and its impact on Hell’s Kitchen, the Netflix-produced series have consistently referenced both the larger film series and the other shows within.

In terms of impact on other shows within the Marvel Cinematic Universe, though, one example stands out. Luke Cage is introduced as a recurring character in Jessica Jones, and the events of that series directly set up his situation leading into his own solo series. Usually, this is the case with a spin-off; a character is introduced in a parent show, then that character proves popular so gets his own series. However, in this case, we already knew that a Luke Cage series was in development from the beginning, so the events of Jessica Jones merely established Luke Cage and his background in preparation.

The tight plotting and links between the Netflix shows is a wondrous thing for fans as they seek connections between the shows, but it does highlight how distant the other MCU televisions shows – namely Agents of S.H.I.E.L.D. and Agent Carter – are from them. While there are some connections such as the biker gang Dogs of Hell appearing in both Agents of S.H.I.E.L.D. and Daredevil, the two branches of the MCU are kept very much at arms length. The chances for crossover between the two television arms looks as likely as the Defenders showing up in Infinity War.

The X-Files

The X-Files

The X-Files makes the list for a very specific reason – the show spawned two spin-offs that had their resolutions incorporated into the main series. The first series was not a direct spin-off per se; Millennium was also created by Chris Carter and featured retired FBI agent Frank Black working as a consultant for the mysterious Millennium Group. The show dealt with similar themes to The X-Files, although often the cases were more grounded such as serial killers, or ritualistic murders. The arc of the series revolved around an impending apocalyptic event scheduled for the millennium, playing on fears such as Y2K and doomsday prophecies that were present at the time. Millennium was not conceived as a spin-off of The X-Files, but was clearly set in the same universe. For example, the character of José Chung had appeared on The X-Files before being featured in Millennium. The show was cancelled due to poor ratings in 1999. In Season 7 of The X-Files, an episode named “Millennium” tried to give fans of the series closure.

The Lone Gunmen is a more straightforward case. Spun-off from The X-Files, The Lone Gunmen was a thirteen episode series centered on the trio of fan-favorite conspiracy theorists Melvin Frohike, Richard Langly, and John Fitzgerald Byers. Despite fan loyalty to the show, it was not renewed for a second season. In Season 9 of The X-Files, the episode “Jump the Shark” featured the Lone Gunmen and their allies teaming up with Agents Doggett and Reyes to stop a biological weapons threat. The episode ended with the three Gunmen sacrificing their own lives to contain the bioweapon.

Neither of The X-Files‘ sister shows had much of an impact on it, aside from the need to incorporate elements of both show’s into the main mythology to provide a sense of closure for fans of both series. How well it did this is up for debate. Millennium fans generally feel that The X-Files episode did not do the series justice, while killing off the Lone Gunmen in their episode proved unpopular with fans of the trio.



Finally, here’s one you might not recall: Cheers. Without Cheers there would be no Frasier. But did you know there were two other shows in the Cheers universe?

The second Cheers spin-off was called Wings and featured appearances by members of the Cheers and Frasier casts during its run, firmly establishing them in the same universe. The other was The Tortellis, a short-lived show about Carla’s ex-husband and his new wife as they moved to Las Vegas.

Mike Delaney
Mike Delaney is Content Team Lead for Fandom's Movie/TV Vertical and specialises in all forms of entertainment. Star Wars fan and general pop culture addict. Only two beverages worth drinking are tea and whisky.