Il film segue la storia di Harold, che usa il suo magico pastello viola per ritirarsi nel suo mondo fantastico, ma ben presto si rende conto che lui è stato egoista con il suo pastello e lo usa per decidere di aiutare i suoi genitori e gli altri, e persino per andare in missione su Marte.
Artful Penny could indeed draw anything she wanted with her magic crayon and it would spring into life. A fantastically useful toy to have. Only her best friend friend Dennis knew her secret so the two had acres of fun winding up adults, nosey-parkers, bullies, bad guys, teachers and ne'er-do-wells with her creations, or solving problems for folk, or sketching their way out of tricky situations. Penny would scribble away, her arm becoming a blurr as she worked and then - hey presto! - her line drawing would leap off the drawing surface as a fully-formed 3D object.
