Tulpas are sort of like imaginary friends that, with practice, you can learn to see and hear almost as well as real people, and eventually they can kinda/sorta think for themselves (though all their perceptions are limited to the insides of your mind, of course). "Tulpa" used to describe a very specific sort of thoughtform used in certain Buddhist practices, but today there are ordinary people trying to manifest tulpas for themselves (as described at link.

Have you heard of tulpas before? What are your thoughts on the phenomenon?