One of my favorite small pleasures that comes with directing is getting to put together the curtain call. It's akin to a little piece of decadent candy for me; small, not terribly important, but immensely delicious and satisfying. Curtain call exists pretty much solely as a reward for the actors, their moment to be acknowledged for their hard work. I also like using it as a way of deconstructing the relationships in the show, composing it in such a way as to display to the sharp-eyed audience member how the character relate to the plot and to each other. And while I guess I put entirely too much thought into it, but as I said, doing it just so gives me a great deal of pleasure.
Here is my theory of how curtain calls are best organized. There are two factors to consider, order and grouping. Order is the procession in which the actors appear, with the most important characters emerging later than the others. As an actor, I've always found it's really an honor to emerging in the last three waves of bows, with the coveted final one the most ego-boosting of all. If (n) is the number of waves of bowing, the most significant characters tend to appear in waves (n), (n-1), and (n-2). I firmly believe that the most significant deciding factor on where to place people is how much influence they have over the course of the plot. Role size I do feel is a factor to consider, but I find it much less important than plot significance. I would rather a smaller character come out later if they matter more to the story-- or if they are a particularly notable part, like Mercutio or Palamon --than strictly gauge by how many lines they have, or by how much time they spend onstage.
Groupings, as in, what combination of people come out at what time, I feel should be determined by character-relatedness, the similarity of the service they provide to the plot. Obviously characters who feature together and are roughly the same size parts should come out to bow together. But that also means that if they're doing the same kind of thing for the story, even if they don't interact much onstage, grouping them together makes sense. For example, if there are two parallel figures who both provide support to the main characters but don't deal much with each other, I like to have them come out together. Opposites-- such as Edgar and Edmond in Lear-- also make sense.
Let's use the curtain call of Romeo and Juliet as an example. I thought having Frances as Tybalt and myself as Paris come out together and fairly early made sense. Even though our characters don't have much to do with each other onstage, we served the same plot purpose-- immediate antagonism --and our roles were about the same size. By contrast, I felt like instead of having the Nurse come out alone in position (n-1) and Friar Lawrence come out alone at (n-3), they should have both come out together at (n-1)-- again, they had the same plot purpose of facilitating the efforts of the two leads, and had about the same time spent onstage. Sacrificing the solo bow I believe would have been worth both of them moved up to acknowledge their significance by the order.
The solo bow is a bit tricky. Normally I only give it to the most important characters (as in, the primary support comes out at wave (n-1) alone, and then the lead comes out at position (n) alone) but it's also a way to acknowledge the uniqueness of a supporting role. I find it appropriate for the fan favorite in a show, such as Palamon in To Think of Nothing, to get a moment for the audience to express their particular appreciation. Sometimes a compromise can be made status-wise by having certain character come out earlier, but alone. The solo bow is kind of an honor, so sometimes you can balance acknowledgement of two different groups' significance by having the earlier wave contain just one person bowing by himself, and the later wave come out with a group. This is what I did with Horatio; he appeared earlier in the order than Laertes and Ophelia, but he got the honor of bowing by himself. And sometimes you just have a character who doesn't go with anyone else in the show, and simply doesn't make sense in any grouping with anyone else.
For HTP, I designed the curtain call for both of the shows I directed, plus King Lear. I only sort of remember what I did with Lear; anyone who wants to remind me is welcome. It was remarkably difficult to design a curtain call for To Think of Nothing because everybody was pretty much just as important to the piece as everyone else. Hell, everyone being constructs of Cassander's brain, everyone literally IS the main character! So I couldn't use my normal formula there. What I settled on was that it would reflect the depth to which each character penetrated Cassander's thoughts. Which meant that even though Damon and Selene are respectively the second- and third-largest parts in the show (at least by line count), I decided they should be the first to come out.
As a side note, I have always been a fan of the "call out"-- when the actor or actors who came out in the previous wave remain just slightly to the side of center stage and make a gesture to "call out" the next wave and sort of present them to the audience as they take their bow. I have used it in the three prior HTP curtain calls I organized, specifically with the last two waves to emerge, with Claudius calling out Hamlet, Cordelia calling out Lear, and Andromeda calling out Cassander. I like it as a concept because it acknowledges the way actors and characters need each other for their plots to be interesting and their performances to be strong. It highlights the fact that Claudius and Hamlet, for example, need each other for the conflict to be meaningful, and the way Frances and Jared used each other's performance to make their own better. The call out allows Claudius to show his gratitude to Hamlet for that, and keeping Claudius present during Hamlet's bow acknowledges his own contribution. It's a moment where the actors actually get to demonstrate out of character, "And we thank each other for working together." I have never actually used it except between solo bows for the last two characters, as a sort of tribute to the lead and to the primary support, but I can imagine other contexts for it as well. Perhaps between a group that is strongly connected to another group, but who's contribution to the show as a whole is of a different nature.
Maybe I am unnecessary overcomplicating things, but I really enjoy thinking about this stuff. It's fun for me. :-)
