Actress Kathleen Quinlan will also guest star in an upcoming episode of SGU . UPDATED!

Victor Garber

UPDATE: GateWorld has learned that French Stewart and Kathleen Quinlan will appear in “Alliances.” We’ve also confirmed that Victor Garber appears in “Seizure.”

Big news in the guest star category, as Syfy announced today some fantastic guest stars for the second season of Stargate Universe. SGU returns on a new night, Tuesday, September 28.

(Beware of some minor spoilers below.)

First up is Victor Garber, who genre fans will immediately recognize as Alias‘s Jack Bristow. His huge list of screen credits also includes Eli Stone, Legally Blonde, The Outer Limits, and Glee. He’ll play Ambassador Ovirda of planet Langara — the homeworld of former SG-1 team member Jonas Quinn.

Langara fits nicely into SGU mythology, since it is rich in the mineral naquadria — the highly unstable power source that enabled the crew of Destiny to dial the ninth chevron and reach the ship from the Icarus planet (“Air, Part 1”). Garber’s appearance will come in episode #15, “Seizure” (which is now filming).

That episode will also guest star Stargate Atlantis vets David Hewlett (interview) and Robert Picardo.

Executive producer Brad Wright told Show Patrol that Garber’s role may become recurring.

French Stewart joins the ranks of cast members from the original Stargate film to appear in the television franchise. Before he was 3rd Rock from the Sun‘s Harry Solomon, he played Louis Ferretti in the 1994 film. (That role was taken over by Brent Stait for the TV series.) You might also know him from guest spots on Charmed, CSI, Bones, The Closer, and many more hit series.

Stewart will play Dr. Andrew Covel, the new head of research at Stargate Command. He will appear in episode 13, “Alliances.”

Stewart joins the elite club of actors who have appeared in both the original Stargate feature film and one of the television series. That list includes actors Erick Avari (Kasuf) and Alexis Cruz (Skaara), who reprised their film roles on SG-1, as well as Richard Kind (Gary Meyers, Lucius Lavin).

Third and finally, actress Kathleen Quinlan will guest star in an upcoming episode of SGU, playing Senator Michaels, who replaced the late Senator Armstrong as the new head of the off-world spending committee. Her list of career credits includes Apollo 13 (as Jim Lovell’s wife, Marilyn),Prison Break, and Family Law. Her appearance is also in “Alliances.”

They join previously announced guest stars Robert Knepper (Heroes, Prison Break) and Julie McNiven (Supernatural, Mad Men), who both play members of the Lucian Alliance in a multi-episode story arc.

Stargate Universe returns to Syfy on September 28 at 9 p.m. (8 Central)! Learn more about the season premiere and the rest of the season (episode titles are in for all 20 episodes) in GateWorld’s always growing Season Two episode guide.

NEXT: The full press release

NEXT >