Three (3) is a Numberjack. She has anthony eyes.
She is one of the Numberjacks which works in the Control Room. Three is always begging to go out into the real world, but the others say she's too small a number. In some episodes she does get to go with other Numberjacks, and sometimes she even goes on her own.
She has many toy shapes which she calls her Beautiful Things. Three also likes making noise and can be a bit annoying to the other Numberjacks, particularly Four (but they still get along)