In the past, when you were a small kid, you may have seen a big picture with lots of people in it and you are supposed to find just one guy wearing a certain outfit. Now you remember?
This is called “Where’s Waldo” in America, while it is called “Where’s Wally” in U.K, and actually many different names in different countries.
Sometime you may want to call your friend Waldo, when he’s in a picture with one hundred people and it is hard for you to spot him/her! 🙂