To unlock the Trailer for MPH, you need to place 5th or better in Regulator, Training and Morph Ball areas in the Single Player part of the game. When you do get 5th or better on each one, it will prompt you to view the trailer. After you view it, you can view it any other time by going to the Main Menu (where it says 'Touch Screen to Continue'), there will be a flashing dot in the lower left corner. Touch that dot and you'll be treated to the trailer anytime you'd like. Use the stylus to hit that dot, because using the Thumb Strap is kind of hard.