A sense of humor that tailors specifically to childish and immature words, often said without any real reason, that is adopted mainly by young children, but can be found with young teenagers as well as few adults
Person 1: stinky willy
Person 2: EHEHEHEHEHHEHEHEHEHEHEHEHHEHEHEHEHEHEHE
Person 1: you have such a poopie bum bum sense of humor Person 2: yup
Penis bum bum is used to describe someone who is both a dickhead and/or ass hole, penis bum bum sounds far less offensive then both of these but means a great deal more.