The only reason I mention this is because my oldest girl loves them- has since she was E's age. So this I know will make her look down on MK. She is taught that weed is bad. I am just shocked that MK is risking her image- they make A LOT of stinkin money off the tweens!

Mary-Kate, meet mary jane.

The former tween-friendly Olsen twin is making her first solo foray into series television, landing a starring role on Showtime's marijuana-happy Weeds.

Olsen will join the critically acclaimed show, about a suburban pot-peddling mom (Golden Globe winner Mary-Louise Parker), for 10 of the 15 episodes in the upcoming third season.

"I'm thrilled to be a part of the show," said Olsen. "It's really an honor to be a part of such a talented group of actors and writers."

The 20-year-old has signed on to play Tara, a goody-two-shoes Christian girl who moves into town and falls for Silas (Hunter Parrish), the son of Parker's character, Nancy Botwin.

However, Olsen won't simply be channeling Michelle Tanner in the role.

E! Online TV columnist Kristin Veitch reports that Tara, who will arrive midseason, starts out as the ideal churchgoer but also has a wild side.

"Weeds isn't your eight o'clock family fare," creator and exec producer Jenji Kohan said. "It's an adult show with adult subject matter, and we're confident Mary-Kate is right for the role.

"She came in and read with Hunter and was absolutely charming and real and seemed like a great fit. Audiences have seen only one side of Mary-Kate, but here we'll see her in a whole new light."

Which isn't for lack of trying.

Olsen first attempted to branch out to more adult fare last year, scoring a part in the gritty Edie Sedgwick biopic Factory Girl, alongside Sienna Miller. Unfortunately, Olsen's performance was all but lost in the editing room. What was meant to be her breakout, or breaking-free, role was whittled down to nothing more than a few seconds as a glorified extra, with Olsen appearing in the flick for just a few seconds in the background of a party scene.

The Weeds role will finally give her the chance to advance her acting career and distance herself from the Olsen twins brand of kiddie fare.

She and sister Ashely tag-teamed as the youngest Tanner on the 1987-95 sitcom Full House before branching out in their own series of child-safe series and straight-to-DVD movies, like Two of a Kind, So Little Time and the instant classic You're Invited to Mary-Kate and Ashley's Pajama Party!

The two last teamed in the 2004 box-office dud New York Minute before taking time off to count their millions, attend NYU part-time and hone their party chops in L.A and New York. Mary-Kate also did a stint in rehab for an unspecified "health issue."

Ashley, meanwhile, will continue her behind-the-scenes work, developingand being photographed inthe clothing line she and Mary-Kate launched earlier this year, The Row.