Squirty shits that often result in eating an Apple before its ripe. Usually come on quickly and without warning. Causing the victim to make a run for the nearest crapper.
Look at that stinky Pedro run, boy must have a case of the Green Apple Quickstep.
Diarrhea. This is a southern term. It comes from people who ate apples when they were green, and not yet red. Then thye would obviously run to the toilet.
"I told that boy he'd get the Green-Apple-Quick-Step from them berries!"
"Man, Mexican food always gives me the Green-Apple-Quick-Step."
Referring to the quick step dance move seemingly taken on by people who have to run to the bathroom with explosive diarrhea. Here say suggests that green apples can induce such a predicament - hence the moniker.
This is popular slang in the medical community when referring to patients who have such a reaction to medication such as lactulose given to patients with liver disease.
In popular culture, this was also the name of a 90's grunge band from Seattle.
Dr. Jason prescribed lactulose to Steve who promptly did the Green Apple Quick Step making it to the bathroom with a photo finish.