"dog's breakfast," which has been British slang for "a complete mess" since at least the 1930s. While no one took the time to write down the exact origin of the phrase, the allusion involved seems to be to a failed culinary effort, perhaps a burned or botched omelet, fit only for consumption by the mouth of last resort, Fido. As a vivid figure of speech meaning something so fouled up as to be utterly useless, "dog's breakfast" can cover anything from a play plagued by collapsing scenery to a space mission ruined by a mathematical error. "Dog's dinner," which seems to have appeared around the same time, means exactly the same sort of disaster, but has the advantage of being attractively alliterative. Both phrases are heard occasionally in the U.S., but are more common in the U.K. and Commonwealth countries.
That bedroom looks like a dog's breakfast. Clean it up man!