Crossover ideas when G4 meeting G5?

Note. We know very little at this point.

7446112
Well, they seem to share the same setting... but we'll probably want to see quite how it works first.

Notably, the Manes met many characters from their own distant past...

7446112
My story has three timelines: the currently unpublished SMP timeline (based on Dream SMP, kind of), the G4, and the G5 timelines. I am planning to cross over the two latter timelines later on, but I'm not at that point yet.