Mickey Mouse is an agent with PI.
That acronym stands for Police International, which makes it sound like another term for Interpol but studying the mechanics of the organization in the mere three adventures we have, that organization is far closer to that of something like U.N.C.L.E.
Mickey Mouse, of course, needs absolutely no introduction. This world-famous diminutive (compared to humans but not when compared to more traditional rodents) has been a staple of visual entertainment since the first time we watched him pilot a vessel in Steamboat Willie back in 1928. His adventures have taken him all around the world as well as deep beneath the ocean surface and even outer space, and have been told on television and in movies, books, comic strips, and comic books for decades.
With regards to his actions which cause him to be mentioned in this compendium, I mention 'mere three' stories because that is all that exist, apparently, of the adventures that this fellow, and his near constant sidekick, Goofy, participate in as operatives. While the annals of this anthropomorphic rodent are legendary, as are the escapades he finds himself in, only three deal with his brief time working for PI.
Mickey (my normal habit of calling the heroes by their last name seems inappropriate here) and Goofy come to the attention of PI after they make the front pages with their capture of a notorious criminal gang (said adventure going untold). PI was in a bit of a bind because the agent they had planned to use for an upcoming mission was unfortunately no longer available (?living?). Wanting a replacement, the leadership sees one of those newspapers and make an offer to the pair. They agree.
After a brief period of training, the two are sent on that first mission and will engage in two more assignments, both requiring bravery and intrepidity before they, apparently, decide that their time as "super secret agents" had come to an end and other exciting but non-'cloak & dagger' thrills awaited them.