Even since the FNAF2 Game came out, there has been a lot of debate on the Mangle's Gender. This is because the Phone Guy in the game referred to Mangle as male and Mangle can be seen in 'Ladies Night' Mode on the Custom Night. So here are some videos from a lot of other YouTube users explain details, theories, and evidence on The Mangle's Gender (and also other animatronic's genders too).
EpicCreeperCake
David Near (AKA TheShadowsBetrayYou)
Smike (smikesmike05)
PrimaPlays
UPDATE: It seems as though Mangle's gender could actually be confirmed. The FNAF 4 game recently came out weeks ago. You play as the child and you walk around in the mini games. In the end of Night 1 mini game, the child will walk into what appears to be a bedroom belonging to a girl. Because it has lots of pink color like on the bed, the lamp, and the flowers. And plus, Mangle is in the bedroom. Mangle seems to have more pink color and no white color anywhere on it.
Mangle happens to be one of the most mysterious animatronics ever. What I mean by that is that there's always something strange about Mangle. Like the radio sound whenever we see Mangle on the camera feed, we see Mangle being the only toy animatronic to return in FNAF 3 as a phantom animatronic (there are no other toy animatronics that have a phantom counterpart), and we see Mangle in "Ladies' Night".
Mangle could actually be female this whole time. I mean, Mangle's the redesign version of Foxy, who is a male. And logically speaking, I could find it weird of how the toy animatronics could change genders since they are the redesigned versions of the original animatronics. But I guess you could say, when they tried to remake Foxy by creating Toy Foxy/Mangle, they might mean that they are trying to make it more kid-friendly by having a new female fox. Some females always have a friendly personality. This would make sense with the fact that the eyepatch and the hook that contributed to the original Foxy's pirate theme have both been removed.
Despite seeing Mangle having a hook in this FNAF 2 teaser, Mangle does not have a hook somewhere in the game. This teaser might probably be only telling us that Mangle serves as a replacement of the original Foxy, who has been removed and put in storage, Plus, they thought the original Foxy was too scary. So the staff tried to make Foxy more kid-friendly by making a female version of Foxy. That would explain more pink on Mangle. And plus, females are less scarier than males if you think about it.
This is my opinion. At first, I thought Mangle was once a male, but I guess we can call it a female now. However, we'll just have to wait for Scott Cawthon to officially confirm the Mangle's real gender.
