Space Mumps is an illness portrayed in Red Dwarf. The illness manifests itself as the afflicted person's head swelling to several times its normal size in an extremely exaggerated way, filled with a mucous-like substance.
However, the Cat gets some comeuppance shortly after - Lister decided to scratch his head to relieve the itching whilst co-piloting Starbug, subsequently making it (apparently) explode in much the same way a blister or abscess would, and covering Cat and himself in mucus/pus. Cat found this experience unpleasant to say the least, asking somebody to shoot him in the head with a Bazookoid.
Lister felt much better after this, and showed no signs of the illness after this incident. (RD: Justice)