Philaster
What are we to make of the strange threesome of Bellario / Euphrasia, Arethusa and Philaster, especially given the gender switch that happens at the end? I'm tempted to say this is some sort of commentary on Platonic friendship being the best basis for marriage or male - female relationships in general, were it not for 1) the fact that Arethusa and Philaster are technically not a "Platonic" relationship (although they seem to trend that way) and 2) Philaster's passing comment about Euphrasia's chosen celibacy: "I grieve such virtue should be laid in earth / Without an heir" (5.5.final page) Does he intend to fix that problem himself? That's it; I'm just wondering.

A King and No King
At the end of the play, Arbaces is beside himself with joy to discover that he is no king and can therefore marry Panthea. Presumably, the audience is supposed to be overjoyed as well since he has shown himself to be so vacillating and, at times, unhinged, and now we all know why: he's not really a king by nature. Yet in marrying Panthea, he becomes the king again (if conventional marriage rules apply among royalty). Are we supposed to feel uneasy about his kingship to come?