text: Characters Dexter (voiced by Christine Cavanaugh in seasons 1–3; Candi Milo in seasons 3–4) is a bespectacled boy-genius who, behind a bookcase in his bedroom, conceals a secret laboratory, which can be accessed by spoken passwords or hidden switches on his bookshelf. Though highly intelligent, Dexter often fails to achieve his goals when he becomes overexcited and careless. Although he comes from a typical American family, Dexter speaks with an accent of indeterminate origin. Christine Cavanaugh described it as "an affectation, [a] kind of accent, we're not quite sure. A small Peter Lorre, but not. Perhaps he's Latino, perhaps he's French. He's a scientist; he knows he needs [a] kind of accent." Genndy Tartakovsky explained, "he's a scientist. All scientists are foreign and have accents...It's not really a German accent. It's just Eastern European." Tartakovsky later declared Cavanaugh's input for Dexter to be irreplaceable as he acknowledged her legacy.
  Dexter conceals his lab from his clueless parents, addressed only as Mom (voiced by Kath Soucie) and Dad (voiced by Jeff Bennett), who never take notice of it. His hyperactive, carefree, older sister Dee Dee (voiced by Allison Moore in seasons 1 and 3 and by Kat Cressida in seasons 2 and 4) delights in playing haphazardly in the lab, wreaking havoc with Dexter's inventions. Though seemingly dim-witted, Dee Dee, a talented ballet dancer, often outsmarts her brother and even provides him helpful advice. For his part, Dexter, though annoyed by his intrusive sibling, feels a reluctant affection for her and will come to her defense if she is imperiled.