The Spy Pen features invisible ink that can only be revealed using the UV black light in the cap.
— Mary Porter Green, owner of Curiosity Zone in Ashburn, Va, told TDmonthly in a July 2013 survey that this was one of her store's best-selling toys.

Each color printed tin contains 10 colored pencils, 10 stamps and 3 inkpads, plus a color 'idea sheet'. Kids press their fingers into the non-toxic ink pads, then stamp their fingertips onto a piece of paper. Kids then can use the included stamps (featuring eyes, dinosaur teeth, and more) and colored pencils to add detail to their prehistoric creations.