Few TV shows have dared to recast a character mid-run-Bewitched did it with Darrin, The Jeffersons with Lioneland the results can be unpredictable. When Roseanne this season replaced the departed Lecy Goranson, as eldest Conner child Becky, with Canadian-born Sarah Chalke, 17, ''some of the mail said, 'You look just like Lecy,' '' reports Chalke, who is taller and svelter and has longer hair. ''Some said, 'You look nothing like her.' And-I'm not kidding- there are many people who don't even know that a change was made.''
Becky's role came up for grabs after Goranson quit last summer to attend Vassar. (Ironically, like Becky, Goranson has since dropped out of full-time college; she's now taking classes at UCLA and hoping for feature-film work. ''She wanted to get more life experience,'' explains Goranson's Chicago agent, Paula Muzik.) After hundreds of potential new Beckys were tested, the search extended beyond U.S. borders, and Chalke, then cohosting the Canadian show Kids Zone, was tapped. Standing in the Conner living room last July for her third audition, she had an attack of nerves. ''Everyone said relax. And I'm thinking, right! Like, I've only watched this show my entire life!'' Chalke credits the cast, and especially Roseanne and Tom Arnold, for making her feel welcome. ''Flowers were waiting for me when I got home. The set is really warm.''
That warmth sustains her when she gets homesick for her friends (no beau though). Chalkewho can seem incongruously serene as the belligerent Beckyis close to her parents, and even asked their permission before getting her belly button pierced. ''It hurt. A lot,'' Chalke says. With Roseanne on summer hiatus, she's back in Vancouver, with mom Angie, dad Doug, and two sisters, ages 18 and 4. Mom jokes that the ''only change in Sarah is I can no longer afford her babysitting rates.'' But she still makes dinner for the family. Now, Becky would never do that.