A trans-dimensional traveler has a bad hair day and nearly destroys the universe.
| Air Date | 20 March 1967 |
| Production Number | 6149-20 |
| Stardate | 3087.6 |
| Gregorian Calendar Date | Sunday, 07 October 2266 23:03:53 GMT Monday, 08 October 2266 02:26:15 GMT |
| Primary Arc | The Multiverse |
| Secondary Arc | Final Frontier |
| Tertiary Arc | n/a |
| See It or Skip It | Skip It… |
| Previously on Star Trek | Order | Next Time on Star Trek |
|---|---|---|
| Arena | Chronological | Tomorrow is Yesterday |
| Errand of Mercy | Air Date | The City of the Edge of Forever |
| Arena | Production | Tomorrow is Yesterday |
| The War Without, The War Within | Primary Arc | Mirror, Mirror |
| Arena | Secondary Arc | A Taste of Armageddon |
| n/a | Tertiary Arc | n/a |
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