10 Best Star Trek Crossover Episodes
7. Defiant
When you find yourself stranded on a forgotten world, only to be rescued 8 years later by your own transporter clone who, you surmise, has also gone and ruined your life, there's not really a whole lot you can do to style that one out.
However, if you're Thomas Riker, you can simply use your middle name, defect to a terrorist organisation, and cash in on your alternate self's luck with the ladies to steal the most deadly ship in your former fleet. Posing as Will, he rocks up on DS9, eyebangs Kira (not the evil one) into giving him the keys to the Defiant, and then sets off to smash up some Cardassian bases.
The episode, neatly titled Defiant, features a great turn from Jonathan Frakes. First playing the charming and just-here-for-a-good time Will Riker, before revealing that he's actually Thomas by... and I can't believe I'm actually going to type this... peeling off the sides of his beard to reveal that he's got an Evil Goatee.
Sisko is forced to buddy up with Gul Dukat to avert a disaster, but not before Mayor Kira decides that the whole 'stick it to the Cardi's' energy is incredibly hot and snogs him.