I had that happen with Rocky and Rumor when they were still in the cage at night and turned over their water, what a mess. It took two of us to hold each one and basically soak their paws in a sink of water and pick out the litter. I also held a wet washcloth around each paw to help soak it off. Once you get it mushy enough you can pick it (or smear it) out. It was a long hard ordeal for us all. They had also flung the water and litter out of the cage all over my kitchen floor and cabinets and it had dried. It took me forever to get it cleaned up and I had company on the way. That was the last night I kept them caged, they became full time in the house kittens after that nightmare.