here's how Wario could have been added in Mario 64, no we are not talking about the Wario apparition. If the player waited infront of the painting until Mario is about to go to sleep, Wario would appear behind Mario (not as a head, but his whole body), and would say,"hey, what's taking you so...
here's how Luigi could have been handled in Mario 64, he wouldn't be playable, but rather a support role, if you had at least 10 stars. go infront of the star statue in the courtyard Duck, and wait for Mario to nod 3 times, then Luigi would appear and say,"hey Mario, long time no see. Bowser...