You could say that professional movie acting is a kind of madness - it's getting paid to dress, speak and behave like someone else, as well as read prepared lines and perform actions at the behest of a kind of despotic puppetmaster (director), all for the entertainment of an audience. Whichever way you look at it, that's just weird.
Of course, for most actors it's just a job, and at the end of the day, most thespians go home and resume their normal lives. For method actors, this is complicated a bit further - a lot of method actors like to remain in character during a shoot - but still, when the end of filming comes, it's back to regular old existence. See, for most method actors, for most of the time, the decision to be someone else for a few weeks stays within their control; it's when they've accidentally started living as the character that it begins to get worrying. And in a few instances, this has - hilariously - actually happened.
Almost as though the character began to seep into their consciousness or the intense preparation drove them completely insane, actors have on occasion confused their own identity with that of the character they were playing.
Here are nine actors who got so into it they actually forgot who they really were.