A Hidden Mickey is a representation of Mickey Mouse that has been inserted subtly into the design of a ride, attraction, or other location in a Disney theme park, Disney properties, movie or other Disney product. The most common Hidden Mickey is a formation of three circles that may be perceived as the silhouette of the head and ears of Mickey Mouse, often referred to by Disney aficionados as a "Classic Mickey". Over time, the term Hidden Mickey has come to refer to a range of possibilities from a more complete representation of Mickey Mouse (such as Mickey mixed in with a crowd or in the background), or a representation of another character (such as the huge hidden Jafar at the Pangani Forest Exploration Trail in Africa in the Animal Kingdom). Hidden Mickeys are found in various Disney media, such as animated films, feature length movies, TV series, or the Disney theme parks. Mickeys may be painted, made up of objects (such as rocks, or three plates on a table), or be references such as someone wearing Mickey Mouse Club ears in a painting. Hidden Mickeys can take on many sizes and forms.
Hidden Mickeys are slipped into animation cels in many Disney animated classics, hidden in architecture and attractions in Disney parks and resorts, and studio buildings and many other Disney-related features.
The first published sighting of a Hidden Mickey was made by Arlen Miller, who wrote an article on Hidden Mickeys for WDW's Eyes and Ears (a Cast Member weekly publication) in 1989. The article listed Hidden Mickeys found in the Disney theme parks. Months later the author was contacted by Disney News for more information, and the resulting article made the news of Hidden Mickeys spread worldwide. Throughout the years, Hidden Mickeys spread in popularity as an underground, pop culture phenomenon. However, Disney management has yet to officially acknowledge their existence. The closest they have come to publicly doing so is offering the Hidden Mickey books for purchase within Disney stores.
In the George Lopez episode "George Goes to Disneyland" there was a contest to see how many Hidden Mickeys a viewer could find. The winner won $10,015 and a trip to Disneyland. The episode was banned due to copyrights and then reaired late in 2011.
"Real" Hidden Mickeys 
A true Hidden Mickey is one that is not meant to be seen immediately, and is usually placed purposefully by a Disney Imagineer or artist in a context that would not normally contain Mickey Mouse. When the shape of Mickey Mouse is used as an obvious part of the design, such as Mickey ears on the top of lampposts, it is considered decorative and sometimes referred to as a "decor Mickey." Additionally, formations of the iconic head and ears have been spotted in nature or even on animals, but they are also not Hidden Mickeys. The general rule is: "Not associated with Disney, not a Hidden Mickey."
Common locations for deliberate Hidden Mickeys include the Walt Disney Parks and Resorts, where they are most commonly found in attractions, stores, and decor around the environment. Although approximately 1000 Hidden Mickeys have been recorded, The Walt Disney Company has never compiled a complete list of all the "known" or "deliberate" Mickeys (whether created by an Imagineer or a Disney Cast Member), so there is no way to confirm or disprove every single Mickey sighting. However, various websites and books list locations of Hidden Mickeys, and usually allow Disney fans to add, dispute, and/or prove the existence of such sightings.
At Disneyland in the Disneyland Resort, it is said that there is an official, deliberate Hidden Mickey on each attraction in the park. They are often hidden within the attraction, on the ride vehicles, or in the waiting area for the line, and even on occasion the introduction safety videos. Those who want to find an official Hidden Mickey on these attractions can search for it at will, or ask a cast member working at the attraction.
Sources for Hidden Mickeys 
While an attempt at a full list would take up too much space for an article of this sort large lists can be found in the above mentioned books or fan sites such as http://www.findmickeys.com/, http://www.hiddenmickeyguy.com/ and http://findingmickey.squarespace.com/. These sites often have sections on old retired Mickeys as well as growing lists of current Mickeys, including Hidden Mickeys found in nature or by coincidence.
The Hidden Mickey phenomenon has been documented in a series of guidebooks by Steven M. Barrett. Each book is arranged as a scavenger hunt, providing clues and hints to the locations of Hidden Mickeys in the various Disney parks and cruise ships; a scoring system allows groups of people to compete in the hunt. The first book, covering the Hidden Mickeys in Walt Disney World in Florida, was published in 2003. There are currently three books in the series:
- Hidden Mickeys: A Field Guide To Walt Disney World’s Best Kept Secrets (ISBN 978-1887140843)
- Disneyland’s Hidden Mickeys: A Field Guide To Disneyland Resort’s Best Kept Secrets: First Edition (ISBN 978-1887140706)
- Disneyland’s Hidden Mickeys: A Field Guide To Disneyland Resort’s Best Kept Secrets: Fourth Edition (ISBN 978-1887140850)
- Hidden Mickeys Go To Sea: A Field Guide to the Disney Cruise Line’s Best Kept Secrets (ISBN 978-1887140898)
The Hidden Mickey phenomenon is also featured in mystery novels and Game/Quest books for all ages, by Nancy Temple Rodrigue. The first and second Hidden Mickey books were co-authored by David W. Smith. The focus of the historical fiction novels are on Walt Disney's life, his accomplishments, and his legacy. The game/quest books involve solving clues and finding hidden mickeys when in the Disney parks.
- Hidden Mickey: Sometimes Dead Men DO Tell Tales!, 2009 (ISBN 978-0974902623)
- Hidden Mickey 2: It All Started..., 2010 (ISBN 978-0974902630)
- Hidden Mickey 3: Wolf! The Legend of Tom Sawyer's Island, 2011 (ISBN 978-0974902647)
- Hidden Mickey 4: Wolf! Happily Ever After?, 2011 (ISBN 978-0974902685)
- Hidden Mickey Adventures 1: Peter and the Wolf, 2012 (ISBN 978-0983397564)
- Hidden Mickey Adventures: in Disneyland, 2012 (ISBN 978-0983397540)
- Hidden Mickey Adventures: in WDW Magic Kingdom, 2012 (ISBN 978-0983397588)
The Hidden Mickey phenomenon is documented in this reference for Disneyland's Hidden Mickeys by Alan Joyce. Organized for quick and easy reference at the Disneyland Resort in Anaheim:
- The Hidden Mouse: A Comprehensive Guide to the Hidden Mickeys of the Disneyland Resort (ISBN 978-1449527174)
See also 
- Sponagle, Michele (November 25, 2006). "Exposing hidden world of Mickey Mouse". Toronto Star. Retrieved 2009-02-07.
- Roseboom, Matt. "Author documents 1,000th Hidden Mickey; Fifth edition on sale". Orlando Attractions. Orlando Attractions. Retrieved 2 September 2011.
- HiddenMickeyEars.com - A Collection of Hidden Mickeys From All Over The World
- FindingMickey.com - Hidden Mickeys & Details of Disneyland Resort, Anaheim CA
- Hidden Mickeys Guide, site of author Steven M. Barrett
- Hidden Mickey Mystery novels & Game/Quest books, site of author Nancy Temple Rodrigue
- HiddenMickey.com The Art of Being a Hidden Mickey
- TheHiddenMickeys.com - One Family's Hidden Mickey Finds
- Hidden Mickey Controversy - Imagineering Disney Blog