Michael Dorn(I)

Made a grand total of 282 "Star Trek" appearances. He appeared in 175 of the 178 episodes of Viaje a las estrellas: La nueva generación (1987), 102 of the 176 episodes of Star Trek: Deep Space Nine (1993) Viaje a las estrellas VI: La tierra desconocida (1991), Viaje a las estrellas: Generaciones (1994), Viaje a las estrellas: Primer contacto (1996), Viaje a las estrellas: Insurrección (1998) and Némesis (2002). He also directed the following episodes: In the Cards (1997), Inquisition (1998), When It Rains... (1999) and Two Days and Two Nights (2002). The 277 episodes of Star Trek he appeared in means he has appeared in more episodes of Sci-Fi Television than any other actor.

But now they have the series down to a real science where it's about an hour.