I have two long haired cats, and last summer we took them to a professional groomers to have them trimmed down a little so they would be comfortable. These cats are usually very sweet and gentle.
Well, I didn't even get home before the groomer called us and very brusquely told us that we had to come and get them. When I arrived, she was covered in cuts and glared at us.
The cats came home looking...patchy. They wouldn't come near us for days, hissed whenever we came too close and peed in my favorite shoes. They continued to look patchy for months, and this year they can just sweat it out.