I Spy is an American children's book series, first published in the 1990s, with text written by Jean Marzollo, and photographs by Walter Wick, from Scholastic Press. Each page contains a photo with objects in it, and the riddles (written in dactylic tetrameter rhyme) accompanying the photo state which objects have to be found. Although the first I Spy book contains unrelated pages of still life pictures, subsequent books are more thematic. Several video games based on the I Spy books are available for Windows PC, Nintendo DS, Wii, iOS, Leapster, and Game Boy Advance, including I Spy Spooky Mansion, I Spy Treasure Hunt, and I Spy Fantasy. These served as early examples of an increasingly popular hidden object game genre. I Spy merchandise has been sold in at least 31 countries worldwide. Wick stated in a 1997 news article, "My career can really be put into two categories: before I Spy and after I Spy. ... The success of the books has been really nice. I never got that lucky break in my commercial career, but all of that hard work ... was usable for I Spy." Source: Wikipedia (en)