Press Select to open the manual, go down to "About NOBY NOBY BOY" in the table of contents and press L2 on it. Then carefully eat the words 'NOBY NOBY BOY' in the title by pressing triangle to move to the front of the screen, and pressing L2 to eat the letters. Make sure to eat them in the correct order and to not eat any other letters. If you mess up just press Select to close the manual and just open it back up and try again.
I have included a video that I made showing how to get the trophy.
Please vote positively if this guide was helpful and feel free to leave a comment if I can improve it in any way.