Star Systems

Leaving aside the formal delineation of a classical or a postclassical style, I'm wondering if one quantitative index of the postclassical film industry is the likelihood that secondary actors appear in major roles in later films. It does not seem to happen all that much in 40s cinema, that I can tell. Character actors have a distinct role and secondary actors remain pretty much anonymous to us looking back historically. The credits of a Hollywood film post-1960, on the other hand, contains several names of future stars down the cast list, to the point where the fun of watching these films is seeing the star as non-star.