One, or 1, is a Numberblocks character with one block. She first appears in her titular episode. She is voiced by Beth Chalmers. One is made up of 1 red block. She has one maroon circular eye and mouth. She also has a gradient that goes from red to maroon limbs. One is very extroverted, sweet, curious, helpful, bubbly, friendly, and childish. She loves finding singular things and normally calls them "one of something", while the other Numberblocks would usually call a singular thing "a something