Four resembles a large, neatly drawn, bright blue numeral "4" with light blue limbs. surreal, He is genderless. He has a squishy, highly malleable body that allows him to break the laws of physics—stretching his limbs, enlarging his body, or bending reality and perspective at whim. Four has a highly volatile, unpredictable, and child-like personality. Four’s relationship with Two (the British-accented, green numeral who hosts TPOT) is a compelling mix of friendly rivalry, and petty-remarks. Ever since the days moved on Four has eventually grown out of his bitter grudge and warmed up to Two. Four is voiced by series co-creator Michael Huang. His voice is incredibly distinct, high-pitched, and slightly distorted or synthesized.

X is voiced by series co-creator Cary Huang. Their voice is incredibly high-pitched, soft, and childlike. X resembles a bright yellow, nearly-drawn letter "X" with slightly lighter yellow limbs. X is genderless, uses they/them pronouns, and is slightly shorter and rounder in posture compared to Four. X is the polar opposite of Four, defined by their absolute innocence, kindness, and submissive nature. X's relationship with Two is much more amicable, peaceful, and cooperative than Four's volatile rivalry.