Chat Noir's civilian identity from the beta premise of Miraculous Ladybug. Originally he didn't have a name, but both community and creator decided Felix as his name.
Supposedly, he was an aloof and cold character, with a string of bad luck occurring around him because of a magic ring currently stuck on his finger. The reason he chased after Ladybug was because he was told that a kiss from her would remove the ring.
His Chat Noir form and Adrien's are very similar, but Felix has shoulder-length Blonde Hair, prominent Blue Eyes instead of green, and a larger Bell on his Bodysuit.
Felix's design and name were later retooled into Adrien's cousin Felix Fathom.