Laura Vandervoort plays Superman's Krypton cousin Kara, a.k.a. Supergirl, on Smallville.

Canadian actress Laura Vandervoort just didn't see Supergirl as a ditsy blond.

A kick-ass blond, sure. But not a ditsy blond.

"The way I portray her wasn't what they originally had in mind," said Vandervoort, who has joined the cast of Smallville this season as Superman's cousin Kara, a.k.a. Supergirl. "They wanted her to be more of a ditsy, Paris Hilton-type. She goes shopping, she breaks into stores, she's walking around naked.

"But I played it kind of stronger, because I thought, little girls are going to look up to her, and I didn't want her to be another one of those girls. We don't need another one of those girls."

The writers for Smallville (Wednesdays A-Channel, Thursdays CW) should be lauded for adjusting on the fly -- pun definitely intended -- when they saw the unique package Vandervoort brought to the table. With her good looks and her second-degree black belt in karate, the 23-year-old Torontonian who also appears in CTV's Instant Star can break your heart and break your bones in equal measures.

"There is the physicality (to the role of Supergirl), so you can't have a Twiggy or a Mischa Barton," Vandervoort acknowledged. "They had every blond in L.A., I'm sure, and Sweden, wherever, coming out for it. All the drugstores were out of blond hair colour.

"But I'm lucky that I didn't go out with the rest of the girls there (Vandervoort merely sent in a tape and hoped for the best). I did my own thing. I didn't get any information on how to do the character. I just portrayed her the way I felt she should be portrayed."

Vandervoort and Tom Welling, the 30-year-old hunk who plays Clark Kent/Superman in Smallville, must work hard to limit the sexual tension when they appear in scenes together. After all, Superman and Supergirl are cousins.

"That was one of the things we had to be careful about with some of the dialogue, to make sure things couldn't be interpreted in certain ways," Vandervoort said. "Tom's a good-looking guy. But we don't hug very much.

"We kind of made a joke about it in a scene that already has aired. It's when we're talking and I tell him who I am. He says, 'Oh, that makes you my cousin.' And he takes a step back. Tom and I were laughing about that, and I was like, 'You have to do that, you have to do that!' "

Vandervoort never was an expert on superheroes as a youngster but she obviously is getting a crash course in the genre.

"My dad would watch the Christopher Reeve movies and I thought those were pretty awesome, and obviously the idea of being a superhero appeals to any kid," Vandervoort said. "But I wasn't really into it.

"I watched Smallville for the first two seasons or so, but then I didn't keep up with it, because I went to university (York) and was shooting my show in Toronto (Instant Star). But I'm learning. The comic-book world and superhero world is completely new to me and I'm still trying to understand it."

Vandervoort certainly has come to understand how seriously fans take the Superman story.

"It's my job to take it seriously, too," Vandervoort said.

Speaking of serious endeavours, if it ever came down to a fight between the two refugees from Krypton, Supergirl -- at least, Vandervoort's version of Supergirl -- would slap Superman silly, right?

"Oh, definitely," Vandervoort said.

Don't test her, Clark.