Before you continue...
"All of her parts and programming were installed, she even has an endoskeleton... but the company just decided to stop their process on making her... which means they didn't finish her... her face." -Phone Guy explaining Kelly's origin.
Kelly is a kangaroo animatronic who was never finished by the company. She was almost finished until they decided to drop making her and left her in the state she was, which was having no face. However, the endoskeleton head is still noticeable and it is not half gone, unlike Withered Bonnie. Her back legs are different from the other animatronics. While most of them contain of three joints Kelly only has two in her legs, and she did have three in her arms however.
Kelly starts backstage with Puppet and Rally. She usually is the first one to move from backstage. After she moves, she'll either go to the dining area or kitchen. To know she's in the kitchen, you will hear faint sounds of pots and pans, as they are not as loud as Chica when she's in the kitchen. After this, she will move to the west hall, and make her way to your office as she does not enter the hall corner. She can be viewed in the blind-spot and can disable the light like Bonnie, Chica, and occasionally Puppet. Failing to keep her out will get you jumpscared by Puppet, ending the night.
NOTE: There is no need for FNaF2 behavior as she is non-existent in FNaF2
The Fazbear's Fright company uses Kelly as a prop, as her endoskeleton is non-functional. However, a Phantom Kelly is existent. The player can view a vent monitor an will occasionally see Kelly in the vent, exiting out of the camera and going to the left side will give the player a Phantom Kelly jumpscare, and then the ventilation runs out.
Out of Kelly, Rally, and Puppet, Kelly is the only "scrapped" animatronic with a phantom counterpart that actually jumpscares the player.
- Though Puppet does have a phantom counterpart, she will simply appear in your office and will bring down the monitor or maintenance panel if the player tries to bring it up.
On rare occasions, Kelly may not leave backstage at all in FNaF1, and Puppet will be the only moving animatronic. Since no matter what, Puppet always moves.