How 'Spock' Caused A Behind-The-Scenes Fight On Star Trek: TNG

Gene Roddenberry originally wanted "Star Trek: The Next Generation" to be far removed from "Star Trek: The Original Series." As such, he provided a set of rules for the series creators to abide by, one of which explicitly stated that the old crew should neither appear nor be acknowledged. "TNG" was supposed to focus on new characters and explore new concepts, but rules are meant to be broken — a sentiment that eventually applied to "TNG."

As previously mentioned, Leonard Nimoy reprised the role of Spock on "TNG." The Vulcan appears in Season 5's "Unification I" and "Unification II" episodes. This gives fans a fun slice of nostalgia while catching up with the character in his later life as he continues his quest to unify the Vulcans and the Romulus.

Spock isn't the only character from "Star Trek: The Original Series" to appear on "TNG," either. Montgomery Scott (James Doohan) appears in Season 4's "Relics," and Dr. Leonard McCoy (DeForest Kelley) is in the pilot, so the rules were broken before the aforementioned behind-the-scenes dispute. Since then, the rule has apparently been abandoned, and the "Star Trek" franchise has embraced bringing back some blasts from the past, much to the delight of fans.