Factors that can cause stress include constant fighting with another cat and a dirty litter box. (cat-health-guide.org)
Plus, we're less likely to fight with our cats over the holidays... so they definitely deserve some bling. (aercmn.com)
Now I'm tired, my dog is fighting with my cat for bed space and since I have neither I think I might be hallucinating and need to hit the hay. (justarsenal.com)