odd behavior when cat rt'd from vet

[spirit3]

Please help! My 12 yr old spayed female, Spirit, ret'd from an overnight visit (no invasive treatments, just needed a urine sample) and now all my cats are acting like they've never seen eachother and are behaving in a hostile manner. Bob is about 2 (neutered male) and Butters is about 4 (neutered male). Bob and Butters are hissing at eachother, Bob is hissing @ Spirit, and Bob is normally the sweetest cat, we usually even say "Bob loves everybody" because he's so good natured! What's going on and how do I fix it?? So far I've just been trying to act like nothing's wrong, Spirit doesn't need any more stress-how can I diffuse this? Any help MUCH appreciated-and thoughts on why they're doing this.

[spirit3]

ok-makes alot of sense!! i just assumed they recognised eachother by site like we do, but that's me projecting human behavior on them. ok-will be patient!! no fur flying yet, just everyone acting like wierdos. Bob saw Spirit this when he was coming out from under the couch (he'd just been relieved of one of my earrings he'd grabbed as a treasure), saw Spirit, hunched up like a hedgehog, and put it in reverse back under the couch! Spirit just looked at him like "what a nut." Thanks for the timely help!!

[Tinabudde]

Ahhh the smell of a stranger and strange place on Spirit has set off a war.  Cats don't like change and just the scent of the vet can bring back bad memories of being spade and fixed.  It would take a couple days for this to die down but if you want to diffuse it fast, wipe all your cats down with pet wipes they sell them in places like grocery stores, pet stores such as pet smart, then they will smell the same.

[opus88]

this is quite typical actually.....your kitty 'smells' like the clinic and the other animals that were there, she frankly doesn't smell like herself and cats recognize one another(also us too) by the scent...
don't worry in a day or two all will be back to normal :-)