Hidden Gag Reel
From the [Special Features] menu, select the [Picture Galleries] option. When this comes up, press [Right] to highlight David's mask and select this to bring up a short gag reel.

Hidden Frames
Go to the scene at the end of the movie when Tom's character jumps off the building. As he is falling, his life starts flashing before him. At this point you have to slow the play down so you can view the images frame by frame. Near the end of the flashback there are several very strange single frame pictures that are impossible to see at normal speed. One is of Tom's character holding a gun (which never happens in the movie) and another is his plastic surgeon in the film giving the camera the finger. Another is of Penelope Cruz's character tied up on the bed, which is strange becuase in the movie its Cameron Diaz's character that gets tied up. There are several others.