Charles Sykes / Invision/AP 1 / 21
Charles Sykes / Invision/AP 1 / 21

Bono fights fearlessly for humanitarian causes around the world, but there's one thing that really petrifies him: Alicia Keys!

At the premiere of the Showtime documentary "Keep a Child Alive" with Alicia Keys on Tuesday in New York, the Associated Press reports that the U2 frontman interrupted Keys' speech and said: "She's scary, isn't she? She's scary!" 

PHOTOS: Stars' good deeds

Bono, 51, added that the mom of 13-month-old son, Egypt, and wife to Swizz Beatz has "lioness energy."

"I was terrified the moment I met her. I was shaking in my boots," the Irish musician and philanthropist said. "I was very moved by her singing of course, but what was interesting was the hard questions afterwards, and I think it's those hard questions that she asks that lead her." 

PHOTOS: Egypt and other famous babes with unique names

Keys, 30, started her charity, Keep a Child Alive, in 2003. It assists those affected by HIV/AIDS in Africa and India. She hopes her documentary reaches out to all those who want to help, including those unable to travel to Africa. 

PIC: Alicia throws her hubby a surprise b-day bash!

"Keep a Child Alive" with Alicia Keys airs on the cable television Showtime channel on Dec. 1, which is World AIDS Day.


Most Inspirational Celebs

Forbes' 100 Most Powerful Celebs

Moonlighting Celebrities