Among the many reasons "So You Think You Can Dance" can count both dancers and couch potatoes among its fans is the way the competition clearly shows its contestants grow from unknown, struggling artists into full-blown stars. But what will happen when the show takes a page from that other network dance competition and puts an A-list actress on the stage? We'll find out Thursday night (July 23), when [article id="1615200"]Katie Holmes performs[/article] a song-and-dance tribute to Judy Garland.

Holmes is performing the number, choreographed by her friend and frequent "SYTYCD" guest Tyce Diorio, to promote the Dizzy Feet Foundation, a charity co-founded by the show's executive producer Nigel Lythgoe, director/choreographer Adam Shankman and "Dancing With the Stars" judge Carrie Ann Inaba. The organization aims to give dance scholarships to underserved children and create an accreditation program for dance schools.

"I can't say anything about it -- all I know is that Katie Holmes is an incredibly talented dancer, singer, entertainer, much more so than other people have gotten to experience," Shankman told MTV News. "And she, having come onto the board of Dizzy Feet Foundation, really helped kick up the profile. And she is really into it; she talks about wanting a place where [daughter Suri Cruise] can go to school."

Kherington Payne, one of season four's top 10 dancers, gave us a hint of what Holmes' performance will look like, based on her own experience with Diorio. "You can expect a fun, spicy Broadway number, that's for sure!" said the dancer. "I've never seen her dance or sing before, so I think it's going to be exciting. ... She's going to have an adrenaline rush like no other!"

Payne, who is making her own transition from dancing to acting as she co-stars in the new "Fame" remake, is happy to see celebrities like Holmes and this week's guest judge Ellen DeGeneres appear on "SYTYCD." "This show has done a lot for the dance community and for dancers. People are realizing that, and celebrities and non-celebrities want to support it."

In addition to his frequent guest-judge appearances on the show, Shankman has also done his part to support the dance community by producing the "Step Up" movies and helming "Hairspray" (which, he pointed out, was once Suri Cruise's favorite movie). And he's certainly noticed the impact dance TV shows and movies have had on would-be b-boys and ballerinas.

"I think that the TV shows and their outrageous popularity ... have really penetrated the households, and everybody can see how hard the kids work, how real the struggle is, how real it is and how beautiful it can be," Shankman said. "And how exciting and also how aggressive and male and athletic it can feel, so it doesn't have this sort of out-there feeling anymore. ... It's just in people's lives."