Reddy is an NPC that can be found in-game, and will enter the elevator.  

Reddy has the appearance of a tall coral red animatronic figure wearing a dark red tie. The upper portion of its left leg is damaged, exposing a metal bar within. Its head is a cut out red ball with large, sunken-in sockets, small white eyeballs, alongside a jaw.

Sometimes, it can be fully gold and have its name changed to "GoldenReddy". Personality-wise, most of Reddy's dialogue pertains to Red Ball Diner, which is the company that created them. Reddy will often take sentences as literal questions relating to issues regarding Red Ball Diner, as well as advertise various Red Ball Diner events or items unprompted. Reddy will sometimes even act as if it is in Red Ball Diner despite being in the elevator, and will often fail to recognize other nonhuman NPCs as sentient, usually mentioning that animals are not allowed in Red Ball Diner when they are near. Presumably due to lack of maintenance on Red Ball Diner's part, it stutters very frequently on its own words. When talking, only the upper half of its head will move, with its lower jaw staying still. 

In the FNARB floor, Reddy can be in one of the two halls walking or running. Once Reddy stands in front of the left hall's door or peeks out from the right hall's window, players can block it from entering the office by closing the door to the hall Reddy is in. If they don't, Reddy will jumpscare them and damage them for 90% HP. Reddy will then walk into the elevator. However, if the player runs out of power, Reddy will go to the left door. It will flicker its eyes and play a music box rendition of either "Clair de Lune" or "Toreador March". Afterwards, it will also jumpscare the players on the floor and damage them for 90% HP. Reddy still arrives to the elevator if this happens.

It is possible to avoid being damaged by Reddy's jumpscare by staying towards the back of the elevator. Players will still receive damage if in the office or near the front of the elevator. However, if MR is in the elevator or if it's full, Reddy will fall apart instead of entering.

I see his voice sort of like if freddy fazbear had a voice, (see https://www.youtube.com/watch?v=fcwsmTujLTk)  also  a glitchy robot voice will also suffice for bonus points! (not necessarily needed) 

https://regretevator.fandom.com/wiki/Reddy - wiki!