I didn't know you could go to the end game without Crono or Magus. I attempted to make him not join the party because I remembered on my first playthrough I didn't like him, but he still came the 2nd time around. This year was my first time beating the game and I did it with a party of Crono, Marle, and Robo I believe it was. It might've been Lucca or Frog instead of Robo.