Sigh...

Yep, my Zozie-Pie went to the vet as soon as I realized what he'd been doing to his fur-sister -- checked urine for possible UTI and blood for possible hyperthyroidism (evidently also causes irritability). Other than being overweight and needing his teeth cleaned, he was the picture of health. (They've all been spayed & neutered since they were just little.)

Zorro's overall behavior hasn't changed; he is his typical weird but charming self as long as Meg isn't around -- plays, cuddles, purrs like a motorboat, everything as usual. This situation with Meg has been more of a gradual escalation than a sudden change, as he's gone from "passive aggressive" to just flat-out aggressive with her.

And Cathy, thanks for the advice about the saline; I was just going by what the vet told me to do the last time he sent Meg home after an abscessed owie, but I can see where it could very well make things worse instead of better -- after all, when the vet told me peroxide, he already had her on antibiotics. I'd imagine the vet will give her another of those handy-dandy antibiotic shots, which is a good thing considering my track record with giving them pills. I seem to have the only cats in the world who won't eat pill pockets -- not even if there's nothing in them!

Man -- pill pockets, Feliway, Clomicalm... all the magic bullets have been shooting blanks here! And I always thought I was such a good cat mom...