Online video, in its initial phases, was populated mostly by unknowns because many stars were reluctant to lend their prestige to an untried medium. Now, though, the ability of celebrities to cut through the clutter means that familiar actors, athletes, comedians, models and singers are being cast for webisodes.

It is “the value of borrowed interest,” said Howard Friedman, senior vice president of marketing for Kraft cheese and dairy at Kraft Foods. An online campaign for Philadelphia cream cheese, handled by Digitas and Eqal, uses Paula Deen, the cook, author and TV host, toencourage “real women” to upload video clips in which they make favorite recipes.

About 5,100 videos have been submitted, Mr. Friedman said, mainly because of Ms. Deen’s ability to “mirror” the personality traits of the customer whom Kraft was trying to reach like being “someone who loves the busyness in her life.”

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Another TV host, Jill Cordes, is to be featured in 36 webisodes of “My First Baby,” created by the Meredith Video Studios unit of the Meredith Corporation for the Graco children’s products division of Newell Rubbermaid. The video clips can be watched atmyfirstbaby.com and on Web sites that parents visit often.

Ms. Cordes “has the understanding of the millennial mom and she just had a little girl herself,” said Kim Lefko, general manager for North and South America at Graco. “She became a natural fit, a natural face, for this project.”

The potential allure of a star for a specific audience was also the reason that the comedian Adam Carolla was selected to appear in Web video for the Klondike ice cream brand sold by Unilever.

“The target consumer is a man, 30 to 45, who has a great sense of humor and loves a great joke,” said Brian Manning, vice president of brand building for United States ice cream operations at Unilever.

“We looked at a number of different people,” Mr. Manning said, but Mr. Carolla was chosen for the videos because “the target recognizes him, he’s well known and he has the right sense of humor.”

The agencies working on the Klondike campaign are Story Worldwide and the Mindshare Entertainment unit of Mindshare, part of the GroupM unit of WPP. The videos can be watched at everymanchallenges.com.

There are, of course, numerous examples of celebrities who flop or fail at peddling products, online or offline. To help counter that, marketers say they seek qualities in the stars they select beyond just being famous for being famous.

For instance, the baseball manager and players appearing in a Web video campaign for the new Dove Men + Care line of products, which carries the theme “Journey to comfort,” are “celebrities, but we wouldn’t have chosen them if they hadn’t had fantastic stories” off the field as well, said Rob Candelino, a marketing director in the United States for Unilever.

The stars of the campaign “are real people on journeys to the point where they are comfortable today professionally and personally,” Mr. Candelino said, “and we’re showing their fans, our consumers, a side of them they would never see.”

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In the first Web video, which began appearing on Tuesday, Albert Pujols of the St. Louis Cardinals talks about his wife, Deidre, and they are shown dancing salsa as they did when they first met. The subsequent videos are to feature two New York Yankees, the managerJoe Girardi and the pitcher Andy Pettitte.

The Dove Men + Care webisodes can be watched at dovemencare.com. The agencies working on the campaign are Davie Brown Entertainment, part of the Omnicom Group; Edelman; and the D. L. Ryan Companies.

Some Web video has star involvement, but only behind the scenes. The actor Seth Green is an executive producer, with the Digital Broadcasting Group, of “Urule” — an interactive reality show to appear later this year on urule.tv — but will not appear on camera.“It wasn’t about creating a celebrity perspective,” Mr. Green said of “Urule,” because “the more you introduce outside elements, the more you take away from the presumed reality.”

“Urule” will offer computer users a chance to vote for six weeks on every aspect of the life of a 20-something who, thanks to a sponsor, Ford Motor, will have a 2011 Ford Fiesta to drive.

And some online video clips make do without stars on either side of the camera. To promote the new Momentum 65 DLX convertible car seat for Evenflo, Bold Studios created a Web series, which can be watched at evenflo.com, that uses actors who are not well known.

“You can borrow the interest from a celebrity,” said Chris Craig, chief marketing officer at Evenflo, “but we hope we can create the interest by the content being relevant or relatable.”