My favorito! is named Alice. She lives in a white room inside my head, and pretty much another me, but she looks different. She's always there, and we talk all the time. She likes to annoy me though. And then some of my other favoritos are named Irissa, Evangeline, Nikolai, and Anya.
Not really imaginary - but I do imagine that when I am talking to my perros that they understand me and are responding. Yeah, I know - my younger brother told me once - most people talk to their perros (or pets) and are not crazy - but when tu think they are responding - that is crazy.