Alyssa Ogawa - 16 (also in Generations and First Contact).Guinan - 29 (also in Generations and Nemesis).Number of episodes (approximate) (examples) Two well-known people that had roles on Star Trek were the NASA astronaut Mae Jemison and astrophysicist Stephen Hawking. Pulaski was given the credit line "special appearance by" for her Season 2 shows, also fewer than that of O'Brien. In particular, Tasha Yar was in 28 episodes, fewer than the recurring characters Guinan and O'Brien. The line between regular cast, recurring character, and a guest star is sometimes a grey area on TNG. Ro Laren is an example of a recurring character that was introduced on TNG, but did not make the leap to DS9.
Main article: List of Star Trek: The Next Generation cast members Enterprise-D Characters summary (examples)