Star Trek: 10 Times Opening Credits Spoiled The Surprise

A fun way to bring characters from different shows together is to remove any kind of stakes. In the previous entry, Riker was told that he wouldn't remember visiting Voyager at all, so the writers could do whatever they wanted with him. Through a slightly different method, the same is true of this entry.

Mirror, Mirror introduced the dark Terran Empire to Star Trek, not to mention Spock's glorious goatee, but that universe would remain conspicuously absent from The Next Generation. It would return in Deep Space Nine's Crossover, then again in Through The Looking Glass. 

In the latter episode, Sisko is captured by the Terran version of O'Brien, who forces him to travel over to the evil universe. There, he meets the rest of the rebellion against the evil Cardassian-Klingon-Bajoran Alliance. The less said about what happens with this version of Dax, the better, but we see a gruff and grumpy Bashir, a version of Rom hell-bent on revenge for the death of his brother and - oh well hello there - Tuvok, who in this universe never darkened the Delta Quadrant's doorstep.

Though this was not Tim Russ's first appearance in Deep Space Nine, it remained the only appearance as his most famous character outside of Voyager until Picard's third season. Fun fact - it is the only time that a member of Voyager's crew was seen in the mirror universe at all.

It was a nice surprise, telegraphed by his name in the credits. Still, the fun of the fact was enough to mitigate this little spoiler.