(First off, let's be clear that I'm using "real" and "imaginary" in the context of the fictional world of the comic strip).

The portion of Hobbes that is real is just an inanimate stuffed toy tiger. Hobbes as a motile, living, thinking being exists entirely as a figment in Calvin's mind, projected into the object of the toy tiger. So Hobbes the toy is real, while Hobbes the being is imaginary.