The Arm is an anomalous extra-dimensional creature.
The Arm is an inhabitant of the red room, also known as "the waiting room", an anomalous extra-dimensional space connected to Glastonbury Grove in Twin Peaks.
The Arm resembles a human man afflicted with dwarfism.
The Arm's motives are incomprehensible and he makes a lot of cryptic statements.
The Arm is odd but polite.
The Arm's voice sounds like he is talking backwards.
The Arm sometimes stares without talking.
The Arm likes to dance.