Richard Dean Anderson's portrayal of Jack O'Neill was a primary factor in the success of "Stargate SG-1," so he had to have a good reason for exiting the show.

Stargate SG-1 had an impressive run in its day. Here are the characters who appeared in the most episodes of the sci-fi series.

Across its 10-season run, SYFY’s beloved hit Stargate SG-1 tackled plenty of sci-fi concepts and tropes — but one of the best was arguably how the show introduced alternate universes to tell ...