What if Cali and Cali did manage to start a two player session?

It would’ve been extremely weird because SBURB does count them as two separate Souls, but with a single body, one of them WOULD have had to die and become their Dream Self. With no Frog Temple in the Session, either, there’s no way back for some weird time loop, so… Maybe they would’ve had to enter the game simultaneously and the Meteor would’ve been split in half?