Why Chekhov star in Star Trek the animated series?

There's a misunderstanding here! Anton Chekhov, the famous Russian playwright, did not star in Star Trek: The Animated Series.

It's likely you're thinking of James Doohan, who played Montgomery "Scotty" Scott in the original Star Trek series and its subsequent films. He also voiced Scotty in the animated series.

While Chekhov's work is renowned, he sadly wasn't a part of the Star Trek universe!