Jonathan's heart attack was not the only element that originated during the filming of season one. The use of kryptonite bullets was shelved during season one for a later date because of the limited number of episodes they are able to produce each season, as well as the writers wanting to find "the right moment" to use this particular plot element. They ultimately settled on season three's "Extinction", about a teenager seeking revenge against everyone infected by the meteors. "Extinction" featured a tie-in with a season two episode; Van McNulty's reason for killing meteor-infected individuals is based on the fact that his father was killed by the bone-morphing Tina Greer in "Visage", when she impersonated Whitney Fordman. Van's father was the military personnel that came to the Fordman house to inform Whitney's mother that he had been killed in action. "Relic" was another episode that featured an element first thought up back in the first season, which was the use of the same actors to play both their present-day characters and their characters’ distant relatives in flashback sequences. It was not used because the crew felt that the audience needed to have more time to become involved with the characters that are featured on the show on a regular basis.