10 Actors You Didn't Know Were In Star Trek

3. Jason Alexander

Seinfeld’s George Costanza was a major Trekkie, and you can see that in the enthusiasm he brings to the role of Kurros, the villain of 1999 Voyager episode “Think Tank”. Alexander plays the smartest creature in the known universe, and clearly takes the role seriously, delivering his lines with an eerie calm that separates him from his most famous TV persona.

Alexander had been holding out for a part in his favourite franchise for a long time, but was aghast to be offered various roles as boring old humans. If he was going to do it, he wanted to do it properly, and in 1999 he got his wish. Three hours in the makeup chair saw him transformed into a rough headed, tousle haired monk-like alien. He describes in interviews the enjoyment he got from parading his disfigured self before his disturbed children, and it’s clear on screen that he’s having a blast.

Alexander’s performance as George is so iconic that he’ll most likely never fully escape the sitcom’s shadow, but it’s heartening that his fame gave him great opportunities like this one - a bucket list moment for the actor.