Star Trek creator Gene Roddenberry wanted to include a younger cast member to appeal to teenage audiences.
[1]: 345 Koenig's modest height, eyes, thick eyebrows, boyish face, and smile were all strikingly evocative of the lone British "Monkee" who captivated millions of pre-teen girls.
After Paramount Television signed Koenig to a contract because of the number of fan letters he received as Chekov, Roddenberry wrote in another memo "Kirk and Spock and the others actually seem rather 'middle aged' to the large youthful segment of our audience.
[1]: 422 Pavel Andreievich Chekov was born in 2245 and is a young and naïve ensign who first appears on-screen in the original series’ second season as the Enterprise's navigator.
His promotion to lieutenant for Star Trek: The Motion Picture brings with it his transfer as the ship's tactical officer and chief of security.
Furthermore, in the film Star Trek II: The Wrath of Khan, Chekov was subject to mind control after being implanted with a juvenile Ceti eel.
A running gag on Star Trek is that whenever Chekov gets into personal combat with opponents stronger than him, he loses the fight: "The Trouble with Tribbles" with Klingons or "The Gamesters of Triskelion" with the gladiator-like slaves/thralls.
A common myth about Star Trek is that Khan recognizing Chekov in the film is a continuity error because "Space Seed", with the villain, was broadcast before Koenig's casting.
Chekov is mentioned in the series finale of Star Trek: Picard as being deceased in a broadcast by his son, Anton, who is serving as the president of the Federation.
When Kirk orders him to put on a red shirt, a brief sting is heard as a closeup shows Chekov's nervous face, playing on the reputation of redshirts in the franchise as much as the character's shock regarding his sudden promotion.
The third film, Star Trek Beyond, was Yelchin's final appearance as Chekov, the film seeing Chekov accompanying Kirk after the entire crew is marooned on an uncharted planet following the destruction of the Enterprise, forcing them to destroy the last of the Enterprise to escape a trap and later work with the rest of the senior staff to restart a long-lost Starfleet ship to escape the planet and defeat a plan to attack the Federation.
Walter Koenig reprised his role as Chekov 12 years after Star Trek Generations in the fan-created series New Voyages episode "To Serve All My Days".