A day after he unexpectedly won the Nobel Peace Prize, President Barack Obama was still just an opening act for a pop star. At the Human Rights Campaign dinner on Saturday night in Washington, D.C., the president joked, "It's privilege to be here tonight to open for Lady Gaga. ... I've made it."

The quip came not long after Obama promised in his speech to the nation's largest gay-rights group to end the ban on gays serving openly in the U.S. military. He also said that he's urged Congress to repeal the Defense of Marriage Act and pass the Domestic Partners Benefit and Obligations Act. "My commitment to you is unwavering," Obama said, noting that some activists have complained that they "don't believe progress has come fast enough."

In fact, a number of leading gay activists have grumbled that Obama's campaign promises about repealing the military's controversial "Don't Ask, Don't Tell" policy and passing domestic-partner benefits have come to naught so far in his administration, and they've urged him to act more quickly on those campaign pledges.

While Obama made headlines with his bold pronouncements, Gaga, who was dressed more demurely than usual for the event in a pouffy, little black dress, black heels and giant round shades, was for many in attendance the real superstar attraction of the night.

During her performance at the 13th annual dinner, Gaga said she was there to "represent those young people who are taking a stand, who are going tomorrow to march with all of us," referring to Sunday's National Equality March. "You are inspiring a tremendous number of young people, and I know that tomorrow is going to be just as memorable as tonight was. And I promise to continue and to love and be loyal, to stand up for and to continue to challenge the world, for all of you. I'm not going to play one of my songs tonight because tonight is not about me, tonight is about you."

The singer then admitted that she changed "some of the words" and a few of the melodies to John Lennon's classic plea for understanding and peace, "Imagine." Tinkering with the lyrics, she inserted references to the 1998 murder of Matthew Shepard, a gay college student whose death became a national rallying cry for hate-crime legislation. "Imagine there's no heaven/ It's easy if you try," Gaga sang in a jazzy croon, "No hell below us/ And only Matthew in the sky." Later she sang, "People of the nation, are you listening?/ It isn't equal if it's sometimes/ I want a real democracy."

Gaga also appeared during Sunday's march, and though she didn't perform, she urged an end to homophobia and misogyny in the music industry and gave props to her "most beautiful gay fans in the world." Wearing black pants, a white tuxedo shirt and black suspenders, Gaga received a hero's welcome and said even with all the worldwide success she's experienced over the past two years, the appearance in front of the adoring crowd on the mall in Washington was "the single most important moment of my career."

Saying she was inspired by the new young generation of gay activists, Gaga told the crowd, "They say that this country is free and they say that this country is equal, but it's not equal if it's sometimes." Then, to make sure they knew she meant business, she added, "Obama, I know that you're listening," then shouted, "Are you listening? ... We will continue to push you and your administration to bring your words of promise to a reality. We need change now. We demand actions now."