Rotten Bonnie is an antagonist in Fredbear and Friends: Left to Rot.
Rotten Bonnie appears similar to Withered Bonnie from FNaF 2 but his suit is warped and distorted from age and a damp environment. Most of his face is caved in leaving only his bottom jaw and left eye. He is also missing both hands, his left foot, and his legs are covered in tears revealing the endoskeleton beneath.
Rotten Bonnie is active in Test Room 02, along with Rotten Freddy, Rotten Chica, and Rotten Foxy. Bonnie will spawn in the office to the player's rear, beginning far away and slowly moving closer. Once Bonnie is close enough to obscure the player's vision he must be repelled by turning the fan on. This will interfere with his detection software and drive him off. Failing to do so in time will result in a jumpscare, causing a game over.
- Rotten Bonnie's face being missing is a direct reference to Withered Bonnie from FNaF 2, who is also missing his face.
- Rotten Bonnie is presumably the same Bonnie from the Training Tapes but damaged due to age and neglect after Fazbear Entertainment closed it's doors.