I am watching a rerun of Law and Order (what woman aged 18 to 55 doesn't?!!), and the DA said "screwed the pooch" about 3 times in court. Bleeaaah. I have always hated that phrase, but always assumed it didn't actually mean what I thought it meant (requisite quote from The Princess Bride: "That word! I do not think it means what you think it means!")
Anyway, it turns out, upon research that it actually DOES mean what you think it means. Double Bleeaaah. The phrase first came into popularity after the book The Right Stuff was published. The original expression was "f**k the dog," military slang for wasting time or loafing on the job.
"F**k the dog" appeared in print for the first time in 1935 and over time the meaning shifted (from wasting time to royally messing up), while the "screw the pooch" wording took the place of the original phrase.
Short Story Long: By the way, no pooches were harmed in the filming of Law and Order.