A bobble hat is the distinctive item of clothing worn on the head of Waldo and many of his followers.
Waldo, Wenda, Woof, Wilma and the Waldo Watchers all wear red and white bobble hats - a white cap with a red bobble on the top and a red turned-up cuff. Odlaw wheres a similar cap, but with a black and yellow color design.
A trail of bobble hats can be seen throughout the pages of The Great Waldo Search. The hats, along with glasses and walking sticks, were left by others Waldos from The Land of Waldos; and as such, several of the Waldos in The Land of Waldos are missing their hats.
In several of the Waldo books characters lose the bobbles on their hats, and the reader is asked to locate the small red balls among the pages of the book.
- The Ultimate Fun Book!, 2 lost bobbles from Waldo and Wilma's hats
- "The Beat of the Drums" -- 1 bobble
- "O, What a Lovely Maze!" -- 1 bobble
- The Magnificent Poster Book!, 10 lost bobbles from the Waldo Watchers' hats
- The Castle Seige -- 3 bobbles
- On The Beach -- 1 bobble
- Military Parade --1 bobble
- Land of Sports -- 2 bobbles
- Among the Pirates -- 2 bobbles
- The Future -- 1 bobbles
- Where's Waldo? (special edition), 1 lost bobble from a Waldo Watcher's hat
- "The Beach" -- 1 bobble
- Where's Waldo Now?, 1 lost bobble from a Waldo Watcher's hat
- "Once Upon a Saturday Morning" -- 1 bobble
- The Fantastic Journey, 1 lost bobble from a Waldo Watcher's hat
- "The Unfriendly Giants" -- 1 bobble
- Where's Waldo? in Hollywood (special edition), 1 lost bobble form a Waldo Watcher's hat
- "The Swashbuckling Musketeers" -- 1 bobble