Yeah sometimes, just like with us, an animal is just 'off' their food for whatever reason. One day of not eating is not terribly alarming, unless the animal is also not acting normal, or having vomiting/diarrhea, or showing some other symptoms. If the hunger strike continues more than a day, and/or in the face of particularly tempting food offerings, then absolutely you need to get the cat to a vet. Cats do not handle going without food well.
He did it again this Sunday. Barely eating, not being his cuddly self and constantly sleeping. While it's not weird for a cat to sleep almost all of the time, he's never sleeping that long when I'm home and when sleeping, he'll try to find a spot on my lap or shoulders. The only reason I didn't call the vet was because he was still eating little bits once in a while and didn't say no to treats (gave only one to test this).
By now he's back being his old self, but he had me worried. It's the second Sunday in a row he was like this and now it also lasted the entire Monday. Is my sleeping in on Sunday throwing him off that much? I sleep in on Fridays too, no problem there it seems...
The vet couldn't find anything. She advised me to keep track of when he's acting weird and to take his temperature those days. Since it happened twice on Sunday we also agreed to lock the cat door Saturday night. Maybe it's all coincidental or maybe it's sort of an infection with a certain cycle, but the vet expected he'd feel bad for a longer period in that case.
No weird Sunday blues for Archie this time. I kept him inside from Saturday evening until Sunday around noon, even then I called him every now and then to check how far he was and he always arrived within seconds (he's neutered and rarely wanders off)