When SG-1 entered its ninth season, Richard Dean Anderson ended his status as star and producer of the series. Instead, he opted to make several guest appearances. Now, much like his character, the former SG-1 star is being coaxed of retirement for a special reunion of the popular sci-fi show.

from Pocket –https://www.giantfreakinrobot.com/ent/richard-dean-anderson-sg1-stargate-episode.html