While I have no evidence to back up this claim I'm sure my anus doesn't look as nice.
Mammatus, also known asmammatocumulus (meaning "mammary cloud" or "breast cloud"),[1][2] is ameteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud. The name mammatus is derived from the Latin mamma (meaning "udder" or "breast"). According to WMOInternational Cloud Atlas mamma is a cloud supplementary feature.[3] http://en.m.wikipedia.org/wiki/Mammatus_cloud