I remember years and years ago (I'm talking ~2000ad) someone wrote a Chrono Trigger screenplay. They essentially made Robo and Ayla (and maybe Frog?) non-party members, only briefly helping the core trio of Crono, Marle, and Lucca.
Now that I think of it, they may also completely skipped over Prehistory and made Ayla a non-character in plot consolidation.