Eddie Murphy Star Trek Casting That (Thankfully?) Didn't Happen
And yes, there really were plans to cast Eddie Murphy for Star Trek.
Back in 80s, when the fourth Star Trek movie was in development, Eddie Murphy was the biggest star whom Paramount Pictures had on their list. His Beverly Hills Cop just ended as the box office winner of 1984. So, the idea to use him for one of the company's established properties was somewhat natural, at least to studio bosses.
But Eddie Murphy eventually rejected the idea, despite being a Star Trek fan himself, and initially becoming interested in the offer.
He even met with producer Harve Bennett and director Leonard Nimoy during early stages of the project's development, and saw drafts of the script, which included a character made specifically for him. But Eddie did not like what he saw and he explained his reasons in his recent appearance on the Jimmy Kimmel Live talk show.
Note that Eddie commented on this issue before, but said that at the time he thought that starring in The Golden Child would be better for his career.
(In the end, though The Golden Child did well in the box office, it was blasted by critics, and largely forgotten.)
Now, however, he provided a different answer:
"Yeah, you know which one it was, it was the one where they go to San Francisco and they get the whales… I was going to be the one that they met when they got to San Francisco, and I was like, "No, I want to go and beam up and be on the ship," so I didn't do it."
Then he added: "Yeah, they had me like talking jive to Spock."
For those readers who are not Star Trek fans and might be baffled, the plot of Star Trek IV involved time travel from 2286 to 1986, and Enterprise's crew naturally met inhabitants of 1986's San Francisco. Eddie Murphy's character was clearly supposed to be one of the latter, rather than a member of Enterprise's crew. And that did not sit well with Eddie, who apparently wanted to be on Enterprise.
After Eddie Murphy dropped out, his character was combined with several others, and given what he said about that character, it was for the best. Star Trek IV achieved critical and commercial success and is now considered to be one of the high points of the franchise.