Some people are pigs; I make them/ Look like pigs (2-3)
To us, Circe sounds like a third grade know-it-all here, or maybe even like Lisa Simpson. She's making a point about the difference between reality and appearances.
Under the care of/ Me and my ladies, they/ Sweetened right up. (8-10)
Up until this point, we forgot (or didn't know) that Circe has ladies-in-waiting. We can't help but think of the showdown between Titania and Oberon in Shakespeare's Midsummer's Night's Dream.
Then I reversed the spell, showing you my goodness/ As well as my power. (11-12)
We're just a wee bit confused here – by turning Odysseus' men into pigs in the first place, isn't Circe able to show him her power? Does she mean, "when I reversed the spell, I showed you my goodness, and my power (again)," or is she just a little insecure about her powerful ways?
Your men with my help braving/ The crying and pounding sea. (16-18)
And with those three little words ("with my help"), Circe involves herself in Odysseus' journey, and reminds him of how much he needs her and depends upon her. How would this line be different if those three little words were not inside of it?
If I wanted only to hold you/ I could hold you prisoner. (22-23)
That Circe! She's a jokester. Her play on words here does make us think about how weird that phrase is to "hold someone prisoner." What do you think is the tone of these final two lines? Why so think the last line alone in its own stanza?