(CNN) Madonna really is the coolest.

The Material Girl surprised 400 fans Wednesday who were attending the 25th anniversary screening of her 1991 documentary, "Madonna: Truth or Dare."

The singer, wearing a fire-engine red, off-the-shoulder dress, was beaming when she showed up at the Museum of Modern Art.

The documentary followed Madonna during her 1990 Blond Ambition World Tour. The film originally premiered at the Cannes Film Festival in 1991, and went on to become the highest-grossing documentary at the time.

Read More