Gif: A CASE OF THE TWINZIES! (Patreon)

Twinfluenza - AKA "the twinzies" - is a rapid-onset condition where two previously unrelated men find themselves transformed into a pair of genetically identical girls. In addition to their physical changes, sufferers typically experience overpowering urges to live together, dress alike and spend a lot of time doing each other's hair and makeup. 

There is no known cure for the condition, and efforts to understand it have been hampered by patients refusing to submit to study. As one of the afflicted put it, "It was weird at first, but now me and my sissi love being twinzies... and there's no way we're ever gonna let you scientist nerds turn us back into yucky ol' boys!"