Walter Koenig reveals he fixed a mistake in a classic episode of Star Trek: The Original Series and William Shatner backed him. Koenig joined Star Trek season 2 as Ensign Pavel Chekov, and it didn't take long for the young Russian Enterprise crew member to join in on the action. In Star Trek: The Original Series season 2, episode 2, "Who Mourns for Adonais?", the Starship Enterprise encounters the Greek god Apollo (Michael Forest), who tries to woo Lt. Carolyn Palamas (Leslie Parrish) into falling in love with him.
https://screenrant.com/star-trek-tos-walter-koenig-fixed-script-mistake/