Firstly, like movies, everyone knows a little bit about medicine. We are exposed to it every day. There are blockbuster movies, like (urgh) Titanic. Hence, there are also blockbuster illnesses such as Cancer and Cardiovascular disease each account for a third of mortality in the developed world. In addition to this, the factors comprising any disease (movie), are infinitely complex, and can be studied down to the most minute of aspects. For example, a possible topic for a thesis may involve a tiny fragment of a receptor on an obscure cell. Much in the same way that one might know the birth place and date of the chief sound engineer on the movie My Best Friend's Wedding.

Some people enjoy specific genres. Some do horror, some do action, others art-house, documentaries or even cartoons. Think trauma, emergency, tropical medicine, research and pediatrics. Every now and then, actors try something from another genre, even playing minor roles. De Niro did The Godfather, De Niro also did Shark Tale. Hence, actors/doctors find the what they like and they're good at. Sometimes a doctor may switch into admin or policy making, in the same way that Tom Hanks did My Big Fat Greek Wedding, or as Zac Braff did for Garden State.

The endless journals and magazines about Medicine detail advances in research, information, trends and reviews of current practice, just as Who, Ok! and Hello! Magazines let us know which actor's doing what and with whom. It may be professional, or it may be discussing the finer points of interaction (perhaps like a new drug's mode of action?). All this information is testament to the constantly changing face of the industry. In fact, some experts focus on just one area; they voraciously digest every scene in one movie or of one actor, memerise the finer points of their work and timing, in much the same way we have sub-specialists in medicine. Just as for the illness, often the ones who know the most about a movie are the ones that have watched over and over again. Chronic illness must be like knowing every line to a movie; you can predict where it's going, the finer points of this or that screen angle.

I guess the challenge to someone acting in a movie for the first time is to watch, learn and absorb the experience. I'm looking forward to clinical rotations.