Students in an Introduction to Theater Production class had an unexpected guest speaker Thursday: actress Emmy Rossum.

Rossum, who has appeared in films like “Poseidon,” “The Day After Tomorrow,” and “Phantom of the Opera,” has been named the celebrity ambassador of YouthAIDS and spoke with students about the organization’s goals of informing youth about the dangers of the disease and to teach them about preventing it from spreading.

“We’re not saying keep your legs crossed until you get married; we’re saying be healthy,” said Rossum, who joked that like many students in the class, she is only 21 years old.

Rossum was wearing a YouthAIDS shirt designed by Michael Stars.

Celebrities are “very important (because) they can use their platform to spread the word,” said Cristina Broker, cause-related marketing coordinator for YouthAIDS. “Kids look to (celebrities) as role models. If I was to get up and talk, they’re not going to listen to me.”

In addition to promoting YouthAIDS, Rossum also spoke to the students about the YouthAIDS Kick-Me campaign.

On World AIDS Day on Dec. 1, YouthAIDS is encouraging people to wear a kick-me sign that displays a slogan promoting AIDS awareness. Interested participants will be able to download the signs from the YouthAIDS Web site.

Students in the class helped Rossum come up with slogan ideas for the kick-me sign like “40 million – size does matter,” “Be positive you’re negative” and “A test you don’t have to study for.”

At the end of her visit, Rossum informed the students that one of the slogans they crafted will be put on a new YouthAIDS flier as well as on the back of a YouthAIDS shirt the organization plans to print specially for them.

The students also received necklaces that YouthAIDS previously sold through Aldo shoe stores to raise money for its ongoing campaign to educate youth about AIDS.

“(YouthAIDS) is a great organization that definitely should be spread around college campuses,” said freshman Sara Hantgan, a member of the class Rossum visited.

“I was star-struck, even though I don’t really know who she is,” said junior Daniel Kenner, another student in the class Rossum visited. “But the fact that she’s here is really cool.”

Beginning last month, the University offers rapid HIV testing for students though Student Health Services, said Marsha Martin, head of HIV/AIDS Administration at the D.C. Department of Health Services. Martin was also in attendance for Rossum’s visit.

“The D.C. area has one of the highest rates for HIV/AIDS infection,” Martin said. “We want everyone in D.C. to know their HIV status.”

Martin added that GW Hospital recently began a pilot program that offers free HIV tests for anyone who comes through its emergency room. Next week the Howard University Hospital will launch a similar program that offers free tests for all its hospitals in-patients.