Brent Spiner appeared in 177 episodes of “Next Generation,” absent only from “Family” (October 1, 1990). Spiner more than made up for his absence, however, by playing Data’s evil twin Lore in four episodes, and Data’s elderly creator Dr. Noonien Soong in one. He played four different Old West characters in “A Fistful of Datas” (November 7, 1992), and an android prototype named B-4 in “Star Trek: Nemesis.” 

Spiner would go on to play ancestors and descendants of Soong throughout “Star Trek,” including Arik Soong in three episodes of “Enterprise,” Adam Soong in five episodes of “Picard,” and Altan Soong in two additional episodes of “Picard.” Data kind of returned for the third season of “Picard” as well, although it was more an amalgam character of all the androids he had played before. That new Data, actually named Daystrom Android M-5-10, appeared in five episodes. 

Marina Sirtis played Counselor Troi in 174 episodes of the show, absent from four episodes in the first season. The writers explained that the character was usually attending psychology lectures. Troi was, however, in three episodes of “Star Trek: Voyager,” still serving as a helper to the neurotic Reginald Barclay (Dwight Schultz). She also appeared in “These Are the Voyages,” as well as seven episodes of “Picard,” an episode of “Lower Decks,” and a “Very Short Trek.” 

LeVar Burton was in 176 episodes of the series, and only went on to appear in five episodes of “Picard.” He also had a cameo in the “Star Trek: Voyager” episode “Timeless” (November 18, 1998). Burton also directed many “Star Trek” episodes, including two of “Next Generation,” 10 of “Deep Space Nine,” eight of “Voyager,” and nine of “Enterprise.” 

As mentioned, Gates McFadden was fired for the second season of the series (a producer hated her for some reason), but she came back in season three. As such, she was only in 152 episodes of the series. She did, however, return for 10 episodes of “Picard,” and three episodes of the animated series “Star Trek: Prodigy.” She also directed one episode of “Next Generation.” 

Wil Wheaton, meanwhile, left the series early on, and only appeared in 68 episodes. He was also in the movie “Nemesis,” two episodes of “Picard,” and eight episodes of “Prodigy.”