I'm guessing that a soap opera star didn't top your list. But, as I found out listening to a recent episode of NPR's Wait Wait...Don't Tell Me, Guiding Light star Tina Sloan ended up pretending to be a doctor on just such an occasion:
I was on a plane coming from Phoenix and there was - somebody had a heart attack. And they came over the PA and said, is there a doctor onboard? Nothing. Is there a nurse onboard? Nothing. I had been a Nobel Prize winning cardiologist on another show. So I went up... I truly did. I truly said to the stewardess, I said, look, this guy's in real trouble. I can say all the right words to him. You know, tell him about his blood pressure and the arrhythmia and calm him down until we get him down on the ground. But I said, you know, I'm not a doctor, but I played a Nobel Prize winning cardiologist.
So Sloan reassured the man who needed medical attention and helped him remain calm while until a real doctor arrived:
I did it. I swear I did it. I calmed him down. And I sat, you know, he was lying down on the ground, and I was talking to him and pretending I was taking his pulse and his blood pressure. And, you know, telling him that he was fine and that he was doing really well. And I did all the things that I was supposed to do.
Of course (and you already knew this), a soap opera star, however talented, is still not a substitute for professional medical attention.
Previously: When the call button calls: A hospitalist's thoughts on delivering care at 30,000 feet, and When the call button calls, part two: Helping four patients in one round-trip transatlantic flight