It depends at which level of detail you are talking about. Stars come in several fixed 'spectral types' which are quite different from one another. On the finest scale, the spectra must be very different depending on the detailed chemical composition of each star, its temperature, density and its state of rotation, its speed relative to the Sun, whether it has an active chromosphere and corona, whether it is loosing mass, and whether it is accompanied by companion stars or planets. All these factors, and many more, cause detailed changes in the spectra of stars.