Mangle was first introduced in "IF FOXY WAS THE PHONE GUY 2", only making a small cameo on the night 3 phone call in the background, but they sounded like a male than her female voice now. This old Mangle voice almost made Eth not release the video.
Overtime, Mangle started to play more games and gained his voice and personality he now has today.
*Mangle actually had two voice changes. In her second appearance when he played night 6 of FNaF 1, it’s voice almost sounded both male and female.
*In almost every thumbnail Mangle is present in, his second Endo head is too, but her second head never speaks. This may because it is just a fake head.
They were a victim of the Fazbear Massacre and became a phantom. Thus, they fell under Springtrap's control and worked to kill the remaining Fazbear residents.
“La la la la la la I like to Dab Dabaw Dab Dab adoon dow Dab Dabaw Dab Dab adoo AHOY MATEYs”