The New York cult rocker is used to having famous Hollywood folk as fans, but was surprised to learn Ashlee and her older sister JESSICA enjoyed his band's music as well.
Fogarino says, "We did a show and Ashlee was hanging out backstage and I really didn't know who she was.
"I asked her what band she was in. I think I embarrassed her more than I embarrassed myself.
"She's so sweet, she's very sweet. I would openly welcome the sisters Simpson into the Interpol fold."