Los Angeles - Will.i.am was left shocked when actress Miriam Margolyes said it was nice to meet him because he is black.
The Black Eyed Peas star looked surprised when the 71-year-old Harry Potter star stared at him during a television interview.
She said on The Graham Norton Show : "I'm just fascinated by you. Unfortunately I don't know many black people.
"We don't get to meet across the colour line much except in showbusiness and that's what's so nice."
Will.i.am was left speechless for five minutes and fellow guest, comedian Greg Davies, tried to relieve tension by saying: "It's exotic."
Host Graham said: "It's lovely, Miriam, you're right."
'I don't know much about rappers'
Miriam - who played Professor Sprout in two of the movies inspired by JK Rowling's books - continued to tell the music producer how she is not used to socialising with people like him.
She said: "I don't know much about rappers, you're the first one I've actually talked to. I was in the musical Wicked and I met a lot of black people and I liked them a lot."
Will replied: "And I'm a black guy. I'm the first rapper and black guy you've kicked it with."
Miriam later asked him if he had ever heard of Jews as she told Graham a childhood story.