All-Purpose Idiot

An all-purpose idiot is someone who is downright stupid and has no idea what they are doing. The term originated from M*A*S*H

(The camp was to be inspected by General Macauthur so Frank was in charge of duty rosters)
Hawkeye: What do you mean no orderlies?
Trapper: They're all out manicuring the rocks, I couldn't even get an X-Ray on this guy.
Hawkeye: Are we running a hospital or a motel for visiting demi-gods?
Trapper: It's Frank Burns the all-purpose idiot.