When Mal makes her confession, when Evie, Jay, Carlos, Dude, and Ben get turned into stone, Ben has a beard and mustache. When the spell is broken after Mal defeats evil Audrey, Ben is clean shaven like he is for most of the movie.
The goof item below may give away important plot points.
When Mal suggests Hades might help because he is her father, the King (Beast) is standing next to her in the room and reacts to her news. Later on, when she makes the public announcement, he acts as surprised as the rest of the crowd.