What a cutie!! Gotta love lops, they have such sweet faces. On the subject of the knotted fur, my bun doesn't like to have her fur brushed and she tends to groom her mats and knots out on her own. Some rabbits seem to mat at the ends of their hair, away from the body. If your rabbits is knotted on the ends of his fur use a mat rake (special comb designed for removing matted hair). A soft brushing will probably take care of his knotted fur. If the hair is matted close to the skin, you will probably need some help from either a groomer or your local vet who provides grooming services. Rabbits with longer fur should be groomed daily to prevent matting of the fur and of course, hairballs.