2-01: Amok Time
When Spock exhibits irrational behavior from pon farr, The Enterprise heads to Vulcan for help.
2-25: Bread and Circuses
Upon investigating the disappearance of the S.S. Beagle crew, the Enterprise encounters a modernized Roman-like civilization.
2-04: Mirror, Mirror
A transporter accident swaps Kirk, McCoy, Scotty, and Uhura from distinctly opposite parallel universes.