My favorite feature in Highlights magazine has always been the Hidden Pictures. I used to do them at the library when I was a kid, and I still do them in my dentist's waiting room. And, yes, besides Highlights, Dr Nick also has copies of the Usagi trades, as well as his cousin Stefan Pastis' Pearls Before Swine collections.
Chuck Dillon is an Usagi reader from way back when Fantagraphics was publishing the individual issues. He would send in fan art for publication. Chuck still does art, but as a professional. He is a very talented freelance cartoonist, and one of his regular jobs is creating those Hidden Pictures for Highlights. He inspired me to do my own, with Usagi. This was printed as the back cover to UY #122, this past summer. I'm doing more of these games. The next one was swiped from Sergio's "Find 10 Things" that used to run in the World Weekly News. Click on the image, and keep clicking on it for easier searching, or keep it small if you want a real challenge.
If you would like to do one of Chuck's hidden pictures, here is one from his very excellent art blog. This one is done in a more realistic style than what he usually does. He does know his polar bear anatomy.http://1.bp.blogspot.com/_BxFC075qvXk/SoM84hMJcGI/AAAAAAAABPY/9yMwWzjjPVw/s1600-h/HP_polarbear_web.jpg
PS-Congratulations, Chuck and Daisy, on becoming new parents!