Barrett started collecting information about the hidden Mickeys in 1999 and wrote the first edition of his book in 2002. These days, most of the tips about Mickeys come in through his website and with discussions with park employees, known as cast members. (Disney is the parent company of ABC News.)
"I get e-mails every day from hidden Mickey hunters," he said.
Barrett personally verifies every Mickey tip he receives. But not every hidden Mickey is legitimate. Some are just regular Mickeys that are clear to everybody -- there needs to be some creativity and work needed to find them. Others might be three circles nearby but not in the correct proportions.
"Sometimes it's wishful thinking; sometimes it's more of a decorate Mickey," he said.
Only about one in every four pans out. If one is questionable, Barrett asks his online followers to vote.
"The voters are usually as discriminating as I am," he said.
And not all hidden characters are Mickey. For instance, in the rocks on the left side of the Big Thunder Mountain exit a Tinkerbell silhouette can be found carved into the rocks.
"The story goes that hidden Mickeys started at Epcot," Barrett said. "When Epcot was being built, Walt Disney management did not want characters in Epcot. They wanted to keep them in the Magic Kingdom. So, the imaginers began hiding Mickeys in Epcot attractions."
From there, they have expanded to the other parks, restaurants and hotels in Florida, California and around the world.
Barrett said going to Disney World helps him deal with his workplace stress and makes him feel like a kid again. But don't assume that when he goes home, he stops thinking about Mickey.
"I dream about hidden Mickeys," he said. "I see them in clouds. I see them off Disney property. I'm looking for them everywhere."