Ever heard of “Six Degrees of Kevin Bacon?” It’s a little game people like to play with celebrities, based on the idea that you can get from any one actor to another (typically the aforementioned Kevin Bacon) by naming someone who was in a movie with another actor, who starred alongside a third in a different movie, and so on, until you make it to an actor who appeared on screen with Kevin Bacon. Today’s Friday Four (well, six, this week) is going to engage in some fun trivia by pulling the sci-fi version of this–counting each jump from universe to universe, how many jumps away are some of the biggest Sci-Fi heroes from each other? Let’s find out!

6. The Doctor and Captain Kirk–Index No. 2

We should probably be glad Scotty doesn’t have a beard.

We’ll start off with an easy one. While we may have missed out on that attempted Doctor Who/Star Trek Enterprise crossover, the new movies have given us some nice connections with the big sci-fi franchise across the pond. The first and most obvious is that Scotty, in the JJ Abrams films, is played by Simon Pegg. Less commonly known is that Simon Pegg was in a Series 1 episode of Doctor Who alongside Christopher Eccleston’s Doctor, “The Long Game.” So, Simon Pegg is the link, connecting Kirk to the Doctor. Simple enough, right? While we’re at Star Trek/Doctor Who connections, We could also do Noel Clarke, who played Mickey (but not in “The Long Game,” unfortunately), and subsequently appeared in the beginning of Star Trek Into Darkness as the suicide bomber working for Khan. This gives The Doctor and Kirk a Sci-Fi Separation Index number of 2 (The Doctor & Pegg-as-Editor > Pegg-as-Scotty & Kirk, giving us two universes total).

5. Ellen Ripley and Korben Dallas–Index No. 2

I don’t blame you if you didn’t recognize him.

While the Alien franchise might have gone down in flames rather violently, the films’ protagonist Ellen Ripley is still an incredibly popular character, played by sci-fi legend Sigourney Weaver. Alien also stars Ian Holm as Ash, and Ian Holm went on to play Father Vito Cornelius in The Fifth Element, an apparently divisive movie (that I love, for the record) which stars Bruce Willis as Korben Dallas. That gives us an Index number of 2: Ripley & Holm-as-Ash > Holm-as-Cornelius & Dallas, two universes total.

Still following? Stick with me, cause these are only going to get more complicated.

4. Malcolm Reynolds and The Terminator (T-800)–Index No. 2

Funny how Connors actually curses less as a teenager.

This one is the first that involves recasting as part of the jumps. Arnold Schwarzenegger played the Terminator, as we all know, sent back in time to kill or protect John Connors, depending on which one we’re talking about. And John Connors, while originally a kid played by Edward Furlong, has been recast several times, and one of those times was for the TV show The Sarah Connor Chronicles, where he’s played by Thomas Dekker. the TSCC version of Connors is protected by another Terminator, Cameron, who’s played by Summer Glau. And we all know Summer Glau as River Tam from Firefly, often sharing the screen with Nathan Fillion’s Malcolm Reynolds.

The Terminator & Furlong-Connors > Dekker-Connors & Glau-as-Cameron > Glau-as-River & Mal, two universes total. (Or three timelines, if you want to get technical.) That’s an Index number of 2.

3. Luke Skywalker and Bill Adama–Index No. 3

Do you think Adama would fall to the Dark Side?

Luke Skywalker, of course, is played by Mark Hamill, who’s had such an amazing voice acting career that he’s perfect for this kind of game. But to reach the universe of Battlestar Galactica, we’ll actually be taking a different route. Instead, we turn to Harrison Ford. His other big sci-fi credit, aside from Han, is Rick Deckard from Blade Runner. Deckard’s fellow officer on the hunt for the replicants is Gaff, played by none other than Edward James Olmos (who we’ve already seen this week). And Edward James Olmos is best known to sci-fi fans these days as Bill Adama from the BSG reboot. That gives Luke and Adama an Index of 3: Luke & Ford-as-Han > Ford-as-Deckard & Olmos-as-Gaff > Olmos-as-Adama, three universes total.

2.Tron and Captain Picard–Index No. 3

Sometimes I forget how trippy Tron is.

The eponymous Tron is played by Bruce Boxleitner, who starred in Babylon 5 as John Sheridan. And also making an appearance on Babylon 5 was Majel Barrett as Lady Morella, a one-off appearance designed to help ease tensions between the B5 and Star Trek fandoms (don’t you just love that that was a thing that required dealing with? Taking that Anti-Trek attitude seriously). Majel Barrett is more commonly recognized as Lwaxana Troi, where she appeared on TNG with Picard a number of times. We could also use her role as Nurse Chapel instead to get to Kirk (or better yet, use Walter Koenig’s role as Bester on B5) or stick with Troi to reach Sisko. If you count Barrett’s role as the computer, practically every Trek character is accessible. That gives Tron and Picard an Index number of 3: Boxleitner-as-Tron > Boxleitner-as-Sheridan & Barrett-as-Morella > Barrett-as-Troi & Captain Picard, three universes total.

1. John Crichton and Fox Mulder –Index No. 4

The disappearance of Farscape One seems like something Mulder would take an interest in.

Farscape stars Ben Browder as John Crichton, and after that show ended, he found himself over on Stargate SG-1, alongside Colonel O’Neill and the rest of the team. One of SG-1’s recurring antagonists was Senator Kinsey, played by a rather prolific character actor named Ronny Cox. Character actors in general are perfect for this kind of game, and Cox has appeared in several of the huge sci-fi franchises over the years, including Trek (we’ve even touched on that before). But the role we’re interested in now is the one he played in RoboCop, Dick Jones, where he’s one of the bad guys. As a result, he shares the screen with Kurtwood Smith, who played RoboCop’s killer, Clarence Boddicker, in the original version. Smith himself has some impressive sci-fi cred, but one of his many roles is Agent Bill Patterson on The X-Files, a fellow FBI agent who looks down on Mulder and his choice of assignments. This gives us our largest set of links yet:

Browder-as-Crichton > Browder-as-Mitchell & Cox-as-Kinsey > Cox-as-Jones & Smith-as-Boddicker > Smith-as-Patterson & Mulder, for a whopping four universes total and an Index number of 4. If there’s a shorter link between the two, I haven’t found it (and I’ve mostly been doing these by hand; the Kevin Bacon “calculators” out there don’t seem to like TV shows).

So that’s all for this week. Can you think of any shorter links between these characters, or have you come up with any on your own? Share your connections and Index numbers in the comments below, or with me on Twitter @RetroPhaseShift using the hashtag #6DegreesofSciFi. I’ve decided to suspend the “This Week in Sci-Fi” posts indefinitely, as they weren’t getting enough attention to justify their existence, but we’ll be back on Monday with the next “What Could Have Been.” See you then!