I hope Panda starts feeling like his old self really soon. He is soooo beautiful. I hope that it is nothing serious. My Maine Coon takes wonderful care of his coat and throws up alot of hairballs on a regular basis but on occasion he becomes very listless and won't eat or move or drink and it always scares me and then the following day, sometimes even two days later he throws up a big hairball. And then he is instantly back to himself and full of energy etc..For some reason, some hariballs are tougher on him than others. I hope that this is all that your gorgeous Panda is dealing with but you know your cat and what is normal for him so I'm glad you're contacting your vet tomorrow. I'll say a prayer for him right now!