Alice has a job she needs done, so she hires Bob. Bob proceeds to do the job, very, very badly, to the point where he creates more problems and often worse than Alice had to start with. The audience will often wonder how Bob ever became a professional whatever. Seen It A Million Times. Distinct from Doom It Yourself and DIY Disaster in that those tropes involve amateurs attempting tasks in which they are untrained, and this trope applies to people who are (supposedly) trained and (purportedly) do for a living.