I just watched the Deep Space Nine episode "Crossover" in which Kira and Bashir find themselves in an alternate universe. Alternate universe episodes are great, and this one was no exception. Kira meets her surlier counterpart. In fact, everyone's surlier in this reality. It's just a surly universe. O'Brien is an exception, and I have to say I really enjoyed Colm Meaney's portrayal of a humbler version of his character.
My favorite part in this episode was the cold open in which Bashir tries to strike up a friendly conversation with Kira. The Major is all business so she keeps her answers short and curt. Finally, Bashir invites her to dinner. She rebuffs him and he tries to save face by insisting that he only intended the invitation as platonic. This is adorable because in the near future (or possibly concurrently) the actors playing these characters would be romantically involved. The episode aired in 1994 and the actors married in 1997. They're no longer together, but it's a cute snapshot.
I'm close to the end of the second season, and I'm looking forward to the Defiant, the Dominion, and Sisko's facial hair.