The Southwest Detective Division said the man took the banana from the counter at Tejada Grocery Wednesday and held it in the front pocket of his hooded sweatshirt, making it appear as if he had a handgun.
Police said the man used the simulated gun to demand money and cigarettes from the female clerk, who handed over an undisclosed amount of cash.
Detectives are asking anyone with information about the crime or the suspect to call Philadelphia Police.
Police received a call at 2:00 a.m. Friday to respond to a one-car rollover, but when they arrived on the scene no one was present. Dispatchers received a call seven hours later from the driver who said he was lost after he got into a car accident that morning. He said he woke up next to some donkeys in a field.
The man said he and his passenger had been drinking the night before and did not remember what happened. Both of the car's occupants sustained several non-fatal injuries.
The driver received multiple citations, but police have not disclosed the specific charges.