Dexter is very short, wears thick semi-circular glasses, and has curly orange hair. He is normally shown wearing black pants, a white zip up lab coat with a black button, purple gloves, and black boots. His skin is pale because he seldom goes outside, preferring his laboratory to normal childhood pursuits. He's not athletic in the least and often suffers the consequences of his physical limitations (victimized by bullies, clobbered in school gym activities such as dodgeball, many objects out of reach due to his short stature.) His initial design was rounder and cuter than his later design, created after his show was revived in 2001; that design was more graphic and stylized, and Dexter seemed much less childlike as a result.
Dexter is the class know-it-all, and prides himself on seldom being proved wrong. This is contradicted by his experiments, many of which are frivolous creations used to achieve ends presented in the show, such as a machine built to render him invisible so as to sneak a look at his birthday presents. He is prone to believing urban myths that he is fed by Dee Dee, which often cloud his judgement, as well as superstitions. Despite his Genius IQ-Dexter is not above cheating when he wants to win-as in the episode "D D & D". It also appears that he knows very little about common illnesses such as Chickenpox. He has many phobias, namely his fear of bugs and clowns. He also struggles to fit in, and the hysteria that potential social situations cause in him constantly gets him in trouble. He has no tolerance for Dee Dee's disregard for his personal space, and will often bellow "Dee Dee, get out of my laboratory!", among other, more extreme measures. Dexter, when shown working, is usually tightening a single nut on an otherwise blank piece of metal or a random machine. He is sometimes shown mixing two chemicals carefully (attempting to pour a single drop into the concoction below), at which point he is interrupted by Dee Dee (usually causing the chemicals to explode). His spiritual mentor is Albert Einstein, and his favorite supehero (who, within the show, is a real-life superhero) is Major Glory.