Teeth Talk
Insert the first disc of the set and in the [Director's Commentary] section, highlight the [On] menu entry. Then press the [Up] arrow key on your remote control. You will now have the chance to witness actor Arye Gross talk about his teeth, which are prepped in a weird monster-like manner.
Hidden Dance
Another one can be found in the [Scene Selections]. On the first page of the selections, highlight the [Next] menu entry and then press the [Up] key on your remote control. This will give you access to footage of Dean and Henry doing a dance on the band stand.
Bonus Violin Scene
The third hidden feature is located on the second disc of the release. From the [Main Menu] go to the [Deleted Scenes] menu. There highlight the [Director's Commentary On] entry and then press the [Up] arrow on your remote control. This gives you access to a scene of Dean's female interest playing the violin.