User blog comment:B214/Question and Answers 2/@comment-4547267-20140410013726/@comment-1359322-20140410085841

Actually the first ones to named Issei Oppai Dragon and Breast Dragon Emperor are the children of the Underworld because of Issei screaming Oppai during the Rating Game between Rias and Sona. Bikou was the one who finalized the name Oppai Dragon and Switch Princess.