1. "The Enemy Within" (evil half of Kirk)
2. "What Are Little Girls Made Of?" (android duplicate of Kirk)
3. "Mirror, Mirror" (mirror universe counterpart of Kirk)
4. and now... "Whom Gods Destroy" (Garth shapeshifting into Kirk's form)

Not that we're <cough>The Undiscovered Country<cough> counting.

At least in this episode they finally found an actor who was hammy enough to play a copy of Kirk, without actually being William Shatner himself.

Transcript

1
Captain's log, Stardate 5718.3. Bringing medical supplies to Elba II, an asylum planet for the megalomaniacally insane.
Kirk: The inmates think they're Napoleon for some reason.
2
{on Elba II}
Spock: This new medicine will cure any insanity, Dr Cory.
Cory: I doubt it, especially for our new inmate, Garth of Izar.
Kirk: The former fleet captain? He was my hero!
3
Garth: Happy to hear it! For I am Lord Garth! This is Dr Cory!
{the real Dr Cory is in a cell, Garth looks exactly like him}
4
Cory: {for real this time} He tricked the guards by posing as me.
Kirk: How?
Cory: He learnt the alien secret of changing his appearance.
Kirk: ... How??
Caption: {pointing at Garth, now in his real shape} Garth's real form. He wears fur.
5
Garth: {now in Kirk's shape} I can impersonate your over-acting perfectly, Captain Kirk! Now to take command of the Enterprise!
6
Garth: {as Kirk} Beam me up!!
Scotty: Queen to queen's level 3.
Garth: No time for this! Beam me up now, you benighted Scotsman!
Scotty: Queen to queen's level 3.
Garth: Right. Just testing. Toodle pip!
7
Garth: {as Kirk} Nooooooooooo!!!!
8
Garth: I will torture your friends!
Cory: Aaaarrgghh!
Caption: {pointing at a green-skinned space babe} Marta. Don't blink...
9
Garth: I will blow up my green-skinned space babe consort!!
SFX: Kaboom!
Caption: Told you.
10
Garth: {as Kirk} I will duplicate you and fight you to the death!!!
11
Garth: {as Kirk} I'm Kirk! Shoot him, Spock!
Kirk: No, shoot both of us! It's the only way!
12
Kirk: Phew. How'd you know it was the real me, Spock?
Spock: Having dealt with duplicates of you not once, not twice, but three times before, it was straightforward. The real Kirk would be the one to rip his shirt in a fistfight.