There's an old saying that you can't go home again. On Wednesday night (April 14), however, Adam Lambert did exactly that and left a worldwide audience welcoming him back with open arms.

"Adam is the King!" read a sign held in the air by an "American Idol" audience member, moments before the season-eight runner-up took the stage in the newest role of his career: music icon. Appearing as a mentor on Tuesday's episode, Lambert reminded the "AI" folks why he's a fan favorite. "There's someone on the stage they're excited about," Ryan Seacrest beamed as he introduced Lambert, who then took over the show. Performing his single "Whataya Want From Me," Lambert was bathed in green light and smoke, like something out of an early '80s new-wave video. It was an appropriate setting, since the song feels like a hit from the heyday of Depeche Mode and New Order.

"Yeah, it's plain to see/ That baby you're beautiful and it's nothing wrong with you," Lambert sang onstage. "It's me, I'm a freak/ But thanks for lovin' me, 'cause you're doing it perfectly."

Wearing a suit, skinny tie and his signature guy-liner, Lambert gave an emotional performance. When he hit the high note at the end of the song, it nearly seemed like he was on the verge of tears.

"Now that's a performance," Seacrest marveled as he stepped onstage after the final note. "Wow!"

"I brought lasers!" the playful Lambert remarked about his retro stage lighting. "I wanted to do something a little different."

With the crowd still buzzing about his show-stopping performance, Lambert went on to say that "Idol" is the perfect training ground for a musical career. "We worked so hard on this show to give everybody a surprise every week," he explained. "Thanks to 'American Idol,' because it prepared me to make it in the real world. I owe 'American Idol' everything."