10 Best Star Trek Crossover Episodes

The universe is, as I'm sure we all know, around 93 billion light-years across in size, when measured from here to here. Just for a bit of context, a light-year measures around 10 trillion kilometers, or roughly the same distance between where BMW drivers park their car, and the actual space they were aiming for.

Yet despite the sheer improbable size of the universe, Star Trek absolutely loves to have familiar faces come across each other in it. Of all the gin joints, on all the space stations, in all the cosmos, she walks into this once that just happens to be run by everyone's second favourite Ferengi. The first is Rom.

And as well as sharing the actual universe, the franchise is in itself a shared universe, meaning that writers are always free to pluck a character from another show and drop in elsewhere if it fits a strong narrative. Or, in the case of Lwaxana Troi, even if it doesn't.

From flying visits to entire bottle episodes, let's look at all the times Star Trek replicated itself a little charachter buffet.

We start with Through The Looking Glass because it might be considered something of a contentious entry. Where the rest of this list has the crossover element front and centre in its story, what we have here is a bottle episode that included a prominent (but not crucial) role, for a star of another Trek. Specifically, Tim Russ as Tuvok.

However, being a Mirror Universe episode, it's got enough of a fresh feeling about it merit inclusion and it's just a fantastic episode in its own right anyway so, here we are.

Kidnapped from DS9 in the opening moments, Ben Sisko is recruited by the Mirror Universe O'Brien to play the role of freedom fighter for the Terran Rebels. His mission; convince the Mirror-version of his late wife to defect to their side or, as Smiley here very delicately puts it, watch her die for a second time.

He has quite the little adventure, too. Socking Bashir right in his whiney moy, and hopping on the good foot to do the bad thing with both Dax and Kira. Not to cancel myself here but this is Mirror Universe evil Nerys and yeah, absolutely fair play on that one.

Oh, and Tuvok's there too!