Terminator: The Sarah Connor Chronicles features two female Terminators: Summer Glau plays John Connor's jealous sorta-girlfriend, while singer Shirley Manson is the world's worst mother. We talked to them about "Octomom," faux-humanity, and girl-fights.

First of all, here's the trailer for the last six episodes of the season that they showed at Wondercon, courtesy of Entertainment Weekly:

Summer Glau's Terminator, Cameron, has been struggling with a lot of stuff lately. She's got a damaged chip in her head. She's got some mysterious agenda we don't fully understand. And she feels threatened by John Connor's new girlfriend, Riley. I asked Glau how she conveys all the stuff that's going on with Cameron.

Glau said the damage to Cameron's chip "threw off her game," and she's been having more insecurity about her ability to accomplish her mission. Plus, she's feeling uncertain because of the new girl in John's life, Riley. All of Cameron's issues are going to come to a head in the last half-dozen episodes, culminating in a huge clash/resolution/change in the final episode.

"Cameron thought she understood herself, and she thought she had an agenda that hasn't been revealed, and when she was damaged, things were going in on her in mind," said Glau. She's also been learning a lot from the people around her. "She's having to question herself," Glau added. "She has weaknesses now." It's been complicated to incorporate all this stuff into Glau's "strategy of playing Cameron."

"I loved the addition of the Riley character," adds Glau. "It gave me an opportunity to ask questions about Cameron's position being threatened."

We also got to talk to Shirley Manson, who said she didn't realize how big her part was when she first came on the show. She thought she might just have a brief appearance and one or two fight scenes. And when she asked Friedman for more details about her character, he said, "I don't know," and admitted they were still figuring out Weaver's whole story. The character of Terminator-turned-businesswoman Catherine Weaver didn't really click, for Manson, until she had scenes with Weaver's daughter, Savannah. After that, she totally understood who this character was, and how she was trying to do a better job of impersonating a human.

During the Wondercon panel, Manson added that she likes playing a bad mom: "Just watching what's happening with "octomom" is an example of how a society views a bad mother, and I relish the concept of playing the machine terminator mum opposite savannah," said Manson. "It's that "hiss factor," when you walk on stage, I welcome that. I love playing a villainess. Having a child there sets it up for great trial and public scorn."

"There was always a certain archness to the Terminators," Manson told us in the roundtables. "You never looked at Robert Patrick and thought he was acting like a normal human."

Manson says Richard T. Jones, who plays former FBI agent James Ellison, has been amazingly generous, taking her aside and basically giving her acting classes on set. They have terrific chemistry together, and "he's a yummy man," says Manson. "There's a joke going around the set that we're going to do our own spin-off series called Weaver And The Man," where Catherine Weaver starts a detective agency with Ellison. (I would actually watch that show.)

"I'm 42. I've been in bands since I was 15," says Manson. "There's a point where you're stepping in front of 100,000 people, and your blood pressure doesn't change. I wanted to do something that scared me." Otherwise, "you just get too comfortable, and everything becomes rote." Playing Catherine Weaver, and having such a huge learning curve as an actor, has given her a huge adrenaline rush. "It gets you back to who you were, before you started to put on the armor... making yourself vulnerable and opening yourself up to new experiences. [It's] the feeling you get, when you learn to ride the bicycle, and you're like, 'Oooh.'"

During the Wondercon Q&A, someone asked who would win in a fight between Cameron and Weaver. "As much love as I have for Summer, I think Shirley would kick her ass," said producer Josh Friedman. And the actresses joked that they have an upcoming scene where they mud-wrestle in bikinis.

Glau is guest-starring in an upcoming Big Bang Theory, playing herself, and she said it was really hard to switch to out-and-out comedy after having only done drama series in the past. The producer of BBT is a friend of Friedman's, and asked him about bringing Glau on the show. "What I love about Big Bang Theory is, those people really know their references. It's smart. It's not obvious" in referencing science fiction and other geek touchstones, said Glau.