Wario's in-universe origins have never been completely explored in the games, however there have been attempts to explore his back-story in various officially licensed comics.

The comic "Super Mario: Die Verwandlung" (which translates to Super Mario: The Transformation) shows Wario merging from Mario as a result of a procedure by Dr. Light to cure Mario from his pixelation.

The comic "Mario vs. Wario" shows that during youth, Mario and Wario, when playing together, would often result in Wario getting either hurt or humiliated, believing Mario to be the cause for his bad luck.

The second comic, "Warios Weihnachtsmärchen" (which translates to Wario's Christmas Tale), a parody of A Christmas Carol, shows a flashback of Wario and Mario as babies building sandcastles but because Wario was mean to everybody, Mario would receive all the attention. Also during a graduation ball, Wario wanted to dance with Peach, Princess Toadstool, however because Mario was much nicer to her she instead danced with him.

While all these comics were officially licensed, they have never been acknowledged by Nintendo. Wario has however appeared as a baby in Yoshi's Island DS.