The Doctor

The Doctor is the 3rd major charactor to appear in the Backroom. He appears as the Silver Bell in the Christmas Edition.

The Backroom

 * Though designed to resemble a head mirror, he ended up unintentionally looking like an eyeball. The Doctor has a glass pane with a hole in the middle.

The Backroom: Retribution

 * In Retribution, the Doctor's design is more accurate, with a brown band around the main body, along with smudges on the mirror.

Personality
Not much is known about the Doctor's personality. However, it is mentioned that he wants to "help". His definition of helping, however, is very different than yours.