10 Weirdest Star Trek Doppelgängers

3. Good Kirk Vs. Evil Kirk

The moment another Kirk appears, with ominous lighting, a maniacal expression and a tonne of eyeliner, you know he's trouble.

In The Enemy Within, a transporter malfunction splits Kirk into two separate versions. The first Kirk contains all the good inside the man: empathy, loyalty, reason. However, a second version emerges unnoticed, embodying darker traits: aggression, selfishness, and cruelty.

'Evil' Kirk wastes no time in getting drunk, prowling the ship like an animal. He viciously assaults Yeoman Janice Rand and thinks nothing of attacking his crew members to cover up his crime. But the 'good' Kirk also struggles, having lost his strength of will and conviction, leaving him indecisive as a captain.

It's a classic Star Trek conundrum. What makes a man? And if all the good is stripped from him, what remains? It's not as simple as it first seems. It becomes apparent that one half, even the good one, can't survive without the other. It's a delicate balance of qualities that makes a civilised person who they are.

It's a complicated predicament. When it's discovered that 'evil' Kirk is dying, 'good' Kirk finds it within himself to literally reach out and take his hand, telling him he doesn't have to be afraid, that he won't let go. Yet later, seeing the ugliness of the traits in his malevolent half, he becomes reluctant to rejoin with him.

After a transporter test to rejoin the two halves goes wrong, Lawful-Good Kirk is even more hesitant to attempt the rejoining. But Spock is adamant that Kirk's intelligence is strong enough to master his fears and complete the meld. While the science behind that particular assertion is a little questionable, it works, and it makes for a suitable metaphor; becoming our best selves isn't about denying our flaws, but learning to master them.