The Rolling Stones' Keith Richards made a new friend the other night -- and it's hard to believe they've never crossed paths.

Keef attended the premiere screening for HBO's upcoming Phil Spector bio-pic on Wednesday, where he made the acquaintance of star Robert De Niro. And how did he introduce himself? By saying, "We have a mutual friend -- Johnny Depp." Depp, of course, co-starred with Richards in a couple of the Pirates of the Caribbean movies.

Richards has another connection to the movie -- long before she married Phil, Ronnie Spector and Keith were an item.