In the autumn of 1951, the 1st Marine Division received a new piece of cold weather clothing: the boot, combat, rubber, insulated or Insulated Rubber Boot. No one called it anything else but “Mickey Mouse Boots” since their outsized shape and black color gave the wearer some podiatric similarity to Hollywood’s famous rodent. […] One hour of inactivity could bring on an attack of frostbite. The standing operating procedure, therefore, for Mickey Mouse bootwear included a provision that each Marine had to dry his feet and change to dry socks at least once a day and preferably more often.
Source: wiktionary