That sounds really, epically bad. You have all my sympathies!
If it's just an emotional reaction, your cat will calm down and be himself again. However, I agree with other posters that a vet visit to check and make sure he's physically well is really important. Sudden changes in behavior are often caused by a health problem, and these is a serious and terrible change in behavior (even though there is the obvious trigger of the strange cat, health problems can make cats more susceptible to other obvious behavioral triggers).
If the bathroom is a comfortable, safe place, with his regular feeding station, regular litter box, and a safe place to hide, it might make sense to keep him confined there to calm him down and mitigate any disasters. However, I don't think being confined in a carrier has any possibility of calming him down at all, and that's what you want; a calm and happy cat. I know taking him to the vet is a very stressful thing, but it's probable there is something physically wrong with him, so it's a necessary step.
Hopefully there won't be any more defecation incidents, but if there are, I wouldn't try to touch him. Even if a cat defecates while sitting down, the worst the (solid feces, anyway) could do would be to get stuck around the rear, right? Getting feces all over usually involves being confined in a small area and sitting on/ lying on the feces, right? So let him do what works, and clean up after him instead of trying to clean him.
You say you're trying to ignore him, but you're putting him into and taking him out of a carrier? Confine him in the bathroom if that works, but don't try to control his specific location (in a carrier or out, ect). Let him be in as much control of his situation as possible.
Good luck! This sounds really, really awful, but being calm and treating it like regular life instead of like an emergency should help. You don't want to set up a feedback loop of unhappiness between Fuzzy and you.
If it's just an emotional reaction, your cat will calm down and be himself again. However, I agree with other posters that a vet visit to check and make sure he's physically well is really important. Sudden changes in behavior are often caused by a health problem, and these is a serious and terrible change in behavior (even though there is the obvious trigger of the strange cat, health problems can make cats more susceptible to other obvious behavioral triggers).
If the bathroom is a comfortable, safe place, with his regular feeding station, regular litter box, and a safe place to hide, it might make sense to keep him confined there to calm him down and mitigate any disasters. However, I don't think being confined in a carrier has any possibility of calming him down at all, and that's what you want; a calm and happy cat. I know taking him to the vet is a very stressful thing, but it's probable there is something physically wrong with him, so it's a necessary step.
Hopefully there won't be any more defecation incidents, but if there are, I wouldn't try to touch him. Even if a cat defecates while sitting down, the worst the (solid feces, anyway) could do would be to get stuck around the rear, right? Getting feces all over usually involves being confined in a small area and sitting on/ lying on the feces, right? So let him do what works, and clean up after him instead of trying to clean him.
You say you're trying to ignore him, but you're putting him into and taking him out of a carrier? Confine him in the bathroom if that works, but don't try to control his specific location (in a carrier or out, ect). Let him be in as much control of his situation as possible.
Good luck! This sounds really, really awful, but being calm and treating it like regular life instead of like an emergency should help. You don't want to set up a feedback loop of unhappiness between Fuzzy and you.
