The term 'Malkovich' comes from the movie 'Being John Malkovich', in which people can visit the inside of another person's brain. It is a go game - usually played on L19 - in which the two players make about one move a day, and describe why they are doing it. Comments by both players and spectators are usually hidden from the players until the end of the game, so as not to influence their thought processes.
On the new baduk server Kaya.gs it is a already implemented feature that are used for a variety of reasons e.g. Giving weaker observers insight into your thoughts behind the move, for making the game review later easier, for the player himself so he doesn't play too fast, for fun etc.
It started with a post - probably in 2008 - by JoazBanbeck on godiscussions that looked like this:
"One of the things that I would like to be able to see is a match between two high dan or pro level players in which they described their reasoning processes prior to making a move. I imagine each player saying something like the following to his audience: 'This group that he threatened can live because of this, this and this ( draws diagram ); so my biggest concern is the safety of this group over here. Now joseki is thus ( draws another diagram) but because of the bleep over there, a less popular joseki like this will be better...etc...etc.' He might take a hundred words or so and a handful of diagrams to describe how he makes the decision.
That's probably going to remain a fantasy.
However, it occurred to me that if I want to see a bit-by-bit decision process that pros use, a beginner would like the parallel opportunity: to see how someone at the high kyu or low dan makes his decision.
(My wife is having two surgeries this month, and I will be stuck at home playing butler/nurse while she recovers. I'm going to be bored. I won't be able to play online because of the constant possibility of interruption, but I will be able to play a slow game. I could put several hours a day into this, but it has to be asynchronous. )
So I'm inviting someone to join me in this. I'm 1D AGA (probably would be 1K KGS if I played online ) You should be about that strength, or maybe one stone stronger or weaker. We would play a match, one or two moves a day, posted in the beginner's forum. Each post would consist of the board diagram showing the game with the latest move, and a detailed analysis - using the 'hide' function - of why we made that move. At the beginning, of course, the comments might be merely that 'It is joseki', and a reference to Kogo or Sensei's lib. In the midgame it might be hundreds of words with half a dozen diagrams."
Some examples are here: http://www.lifein19x19.com/forum/viewforum.php?f=26
ajs3: I would like to do something like this, except with the players openly stating their reasoning and motives as they play. It would be a "learning game" (as opposed to a "teaching game"). I assume that pros understand each others' moves; why then should amateurs care for secrecy? Perhaps it could be called a spiel game.
topazg: Yeah, quite a few of the Malkovich games have been "open", where people have tagged comments (hidden) as spoiler when they give away specific lines, but with no restrictions to being allowed to read each other's thoughts and comments. It works quite well, and is my preferred way of doing them :)
saxmaam?: OGS (www.online-go.com) has Malkovich log available for all of its games.