Doorbot guards the Boring Door that is the entrance to Robot Infrastructure. His job is to keep all non-robots out, and he takes his duty very seriously.
However, he is not infallible, and was once tricked by a Antimony's.of
Antimony puts on antennas to make herself look like a robot, this as well as saying that a robot cannot lie convinces Doorbot to let her inside.
Doorbot is later seen again onwhere Annie yells for him to open while she comes running, which he does.