Back in the day, an advertisement for some hemmorhoid ointment or headache medicine used to feature a guy in a white labcoat who started his pitch with the line, "I'm not a doctor. I play one on TV." Then he'd go on to give his non-medical opinion about why you should buy the product. I don't know why the ad guys thought this would work. Maybe it was some "People hate know-it-alls so they're more likely to listen to an idiot with newscaster hair" thing.
But as far as I know the guy never actually started trying to write prescriptions or perform surgeries. Unlike Amatabh Bachchan and Amir Khan, who are now claiming not only to play farmers on TV, but to be farmers who deserve the right to buy agricultural land. Apparently, they ARE good at spreading manure.