Tibetan Buddhism has a rich and ancient mystic tradition that includes techniques for creating something called a tulpa, also known as a thought-form. The idea is that a properly-trained, sufficiently-enlightened mystic can use intense and prolonged mental effort to give objective physical reality to any object or creature he can imagine.
Alexandra David-Neel, when she traveled in Tibet in the 1920s, reportedly studied this technique and created her own tulpa over the course of a few months. In her autobiography she says that she eventually succeeded in creating a being (a stout, balding monk character) that other people could perceive independently- she didn't tell her traveling companions about her little experiment until afterward, but they still began to ask questions about the "stranger" that had recently joined their camp. She eventually had to reabsorb her creation when it began to act independently and make a nuisance of itself.
Roberta (and everybody else), what do you think of this idea? Are tulpas real? Can people actually create beings or objects this way?