Due to my own conflicting vacation plans, Rachel and I were cast in the same two roles (Gregory and Servant 1, on the minor side of importance) so that during the two weeks I was gone--during run-throughs no less: am I crazy?--Rachel would be able to run our roles on her own. For performances, we would alternate nights, one of us playing Gregory one night and the servant the next, etc.
Unfortunately, once the servant parts had been doled out, Gregory and Servant 1 actually ended up appearing in most of their scenes together, making it harder for Rachel to cover the majority of our two roles in my absence. From what I can tell, the cast dealt with it marvelously (as far as the show's concerned--I know the emotional state of my fellow actors was excruciatingly destroyed after two weeks of no Kirin), but this also added another layer onto Rachel's and my own personal experience.
It is difficult to switch roles from night to night. More work has to go into the actor's journey, because the actor is forced to maintain more and often completely different emotions and reactions. However, to switch roles within scenes every other night presents its own difficulties entirely. Much more work has to go into the sheer organization of each role; entrances and exits must be carefully catalogued, blocking must be distinctly remembered, and the order of everything has to be carefully ingrained--and that doesn't even include memorization or character work.
But Rachel and I have worked together fairly well. From the beginning, we had an amiable agreement about how rehearsals should go, most obviously with us alternating in and out of roles even during the earliest rehearsals. When it got closer to my departure, Rachel was more than happy to let me take over most rehearsals, and was just as ready to inform me about any changes that had been made once I got back. Most of the discretion has been left up to us, so here and there, she and I have had conversations about tweaking a few things to make it easier on ourselves, or deciding which role the added-in lines go to, etc. The hardest part for the both of us occured during my absence, of course: I was standing in a veranda in Italy, doing my best to work through scenes by myself and memorize the order of scenes without watching them, while Rachel was stuck attempting to pick up the slack of an extra part while still having to maintain whatever role she was actually playing in rehearsal.
Now, as we head into R&J performances, I think the both of us have gotten the order and character work down; both dress rehearsals went smoothly for us. This just means all of our show attendees have to come twice, and that is definitely not a bad thing.