Usher pulled off his Broadway debut without a hitch---well except for Cassie's Me & U ringtone going off on an audience member's phone.

" I gotta get in Clive Davis' a--," Usher said after the show, on the red carpet of his afterparty at Manhattan's Nikki Beach. "His phone was ringing right in the middle of the play. Can you believe that?"

Davis, the legendary music mogul, would later say with a smile that Usher was surely kidding — and he doesn't even have a phone. "If I had a phone, how could he tell it was me?" he asked. "

Celebrity (Mario & Bryan Barber) reactions:

"I was very impressed," said "Idlewild" director Barber said of Usher's performance. "He was very convincing. I love what Usher brings with his vocals."

"It's something I will remember 10 years from now," Mario said of seeing his friend on a Broadway stage, calling the performance "effortless." "I'm enjoying that he respects the art of it."

Labels: Mario, Usher