Jeremy Piven and Miley Cyrus are new BFFs. Say it isn't so!

The Entourage actor, 45, and the former Hannah Montana star, 18, became close friends while filming their movie So Undercover in New Orleans.

While promoting his latest film I Melt With You at Sundance, Piven tells E! News:

    "I think I must be an 18-year-old girl because we got along really well. It was just so much fun. I had so much fun with her and we had great chemistry. It was really really weird -- we're like polar opposites."

As for Miley's recent controversies, including her salvia incident last year, Piven adds:

    "You know, you can judge her, but what were you doing when you were 18? She's kind of amazing. There's something so incredibly refreshing about someone who is exactly who they are. There's nothing pretentious about her. She's this force. She loves to laugh."

Um, ok. I guess the old saying is true ... opposites attract.