You will often find a single character in platform games which has to handle everything alone in order to go through the level. Except that sometimes you have to go through a door and press a switch at the same time! And there it gets stuck....
This is why there are cloning game in which your character has the ability to clone himself. And this will be useful to perform specific actions. Sometimes you will just have one clone but it happens that the hero has many clones, such as in Making Monkeys.