Quite consistently, when we come home from their yearly checkup, my girl-cat Hazel gives her brother Harry a thorough cursing in cat -- spitting, growling, a few "stay away from me" pounces and swipes. It seems to take a day or so for her to forget she's mad at him. Treats aren't enough; until this wears off she's very defensive about her bowl, when normally they just check to make sure I've divided fairly and clean up after each other without arguments.
I've been assuming that this is because she doesn't want to be mad at me, and poor Harry becomes the target for her frustrations. ("This is all your fault!") But it could also be that Harry still carries smells from the vet's office or something of that sort.
Harry seems as confused by it as I am.
If anyone actually knows what's going on in that fuzzy little brain, or has tips for how I can could smooth this over more quickly...?