10 Best Sci-Fi Movies Starring Star Trek Actors (That Aren't Star Trek)

First appearing in the 1967 episode, 'Space Seed', Ricardo Montalbán's Khan Noonien Singh is one of the series's most ruthless and iconic villains. A human with genetically enhanced strength, resilience and lifespan, Khan is awakened from suspended animation by the crew of the Enterprise and later exiled for attempting to take command of the ship.

Some years after this, in 1971, came the third instalment in the Planet of the Apes series, Escape From the Planet of the Apes. Montalbán plays a kindly circus owner named Armando, who befriends the runaway apes Cornelius (Roddy McDowall) and Zira (Kim Hunter) and shelters them long enough for Zira to give birth to Caesar, the future leader of the ape uprising. In the following year's sequel, Conquest of the Planet of the Apes, the role of Armando is extended to Caesar's foster-father after the deaths of his parents, making him a major influencing factor in the eventual rebellion.

1982 saw Montalbán return to Star Trek for the film, Star Trek II: The Wrath of Khan, which takes place fifteen years later and explores Khan's revenge plot against Captain Kirk for exiling him.