What Could Have Been: In 2006, Project 51 Productions acquired film rights to produce a straight-to-DVD animated film based on Castlevania III. Simply titled "Castlevania Dracula's Curse", it would have been written by Warren Ellis with art direction by James Jean. Since the project hadn't been updated since 2008, it is presumed cancelled. It has since been theorized to have been rebranded as the upcoming (as of writing) Netflix series.
Fanon: Some previews in Nintendo Power and elsewehere lead to the impression that the three companions are ghosts, and when you hit select you're actually giving them control of Trevor's body. This does seem to make sense given that you defeat both Grant and Alucard in combat, and Sypha emerges from a petrified state. This is Jossed by the various endings of the game, however.