Eliza Dushku plays Echo as Fox begins the second season of 'Dollhouse'. (Fox)

Playing a character upon whom a new personality is imprinted on an almost weekly basis has its own set of challenges.

But it’s surprising to find exactly which personality Eliza Dushku was challenged by most in her lead role on Fox’s sci-fi series Dollhouse (today, 9 p.m., WFLX-Channel 29)

“Playing a mother was something I certainly hadn’t expected,” said Dushku, now in her second season playing Echo. “I’m an auntie and I love other people’s babies and children, but playing a mother and trying to tap into that maternal instinct was challenging.

“Mother was harder than the serial killer/sorority girl. Maybe that says something about me!”

It certainly says something about the faith Dollhouse creator Joss Whedon has in Dushku. Echo has grown from a blank slate into a character dealing with having all of her personalities downloaded into her brain at the same time.

“Last season, Echo had all these personalities downloaded into her, and they aren’t going away,” Dushku said. “As we pick up this year, she’s still tapping into these personalities.”

Friday, Dushku's character Echo is imprinted as a mom, but apparently takes to the part too well. (Fox)

A major reason why Dushku has been entrusted with this evolving part is her history with Whedon. They worked together on Buffy The Vampire Slayer, and Dollhouse grew out of a lunch they had together where, as TV Guide wrote in 2007, she persuaded him to return to TV.

The result has been a show that has grown in popularity as the quality of the episodes has blossomed.

“We don’t have as much of the ‘dumbed-down doll Echo,’” Dushku said. “We have the core Echo, a sum of all her parts, and yet not really all of them.”

As a result, despite being stuck on Friday night, usually a graveyard, Dushku says fans are finding the show, whether live or through their DVRs.

“I can see how they can say that viewers found the show last year, so they may as well leave it where it was and hope that continues,” she said. “There are many shows on TV that are instant hits. We are not that, but we have a core following, and I think people who check the show out and aren’t intimidated by it find themselves being sucked in.”

Those who do end up checking the show out will see a slew of familiar faces — especially to those who’ve followed Whedon’s career. Summer Glau (Firefly, Terminator: The Sarah Connor Chronicles) and Alexis Denisoff (Angel) will play major roles this season, and fellow Angel star Amy Acker will also continue her role at times.

They will also see Dushku continuing to try on new parts, even as Echo grows into a character of her own. And that means occasionally odd adjustments for the actress.

“Trying to breast-feed someone else’s baby is difficult. I’ll just leave it at that!”