The phrase "raining cats and dogs" was invented by James Milner. He was passing the old Datsun cars factory one day and farted, causing the factory to explode horribly. As he was standing with the wreckage ofthe factory and its contents falling around him, he commented "Ay up, it's raining Datsun Cogs".
Unfortunately, during the translation from Yorkshire to English, the phrase was slightly misunderstood.