Yeah, been awhile since I did one of these but this was one I had to talk about eventually. I loved this plot device when I was young, even though it is completely ridiculous. In real life Amnesia is memory loss due to a severe head injury, and can last for an unspecified amount of time.
On TV, not only does amnesia come about through simple bangs on the head but the amnesia can do all kinds of fun things. Sometimes it causes memory loss, but other times it can cause radical personality shifts so that people will think they are totally different person! I suppose it is a clever way to see a character in a different light, but it's used so inaccurately! The best part is that the solution is very often to bang the person on the head again. In real life I really don't see how that would do anything more than make the head injury worst. But in sitcoms, it's a cure all which instantly restored the persons memory and or original personality.
I will never forget being in a Psychology class and the instructor brought this up, and started to get so irrirtaed. I guess I can't blame him, not enough this is everywhere but it's almost always used wrong!
Now before I list the sitcoms that have done this, I have to mention the other TV genre which really beat this to death. That of course is Soap Opera's! I mean amnesia is such a favorite plot device! I don't even have to list the shows, just name a soap opera and I will bet anything there was an amnesia strory line at some point. This goes for daytime and primtime soaps. Amnesia is used more than the evil twin plot device,which I could do another whole article on!