Rose O'Donnell, Susan Boyle

Underneath Susan Boyle's frumpy frock and frizzy curls, Rosie O'Donnell sees a giant green ogre — "Shrek comes to life," in the words of the actress and former talk-show host.

Don't start with the pot-calling-the-kettle-black comments yet. The outspoken comedienne, who has endured her own share of body-image slams, was trying to be complimentary, as she was one of the millions who marveled at the Britain's Got Talent contestant's sensational rendition of "I Dreamed a Dream."

"That moment is what every artist tries to capture," O'Donnell tells People. "Here is this freaky miss, a fat, ugly girl, like Shrek comes to life, directing energy towards her soul. This was so rare ... something authentic in a world that is usually manufactured. It was a perfect moment which will never happen again."

The poignant performance not only transformed Boyle, but also the usually caustic Simon Cowell. "He showed his humanity, and I actually liked him," O'Donnell says.