Euph, why should I tell you all the sneaky secrets?!! My my... does your menu-ing program offer explicit NEXT and BACK buttons for, say, a screen full of chapter-marks? And the chapters have icons or snap-shots?
If someone left the Next and Back buttons highlighted - and obviously functional, but never once displayed the truly-functional Play button (ie, making it invisible), then a User might not know a Play button existed. "I see Next and Back, but nothing else..."
This would be most effective if I had, say, 4 screens' worth of Chapter-Mark Icons, and the Play button might only be installed on Screen 4. Screens 1,2,3,4 would all have Next and Back functions displayed, but only Screen 3 would have Play invisibly colored.
The snapshots-chapter icons might also have single letters or numbers, and might give a clue to correct viewers.
Just imagine setting up a card-trick except using chapter-mark icons, or multiple screens and imagine how confusing Displayed Functions are compared to undisplayed possibilities.
It all depends on your menu-ing program, of course.