Dora Winifred “D.W.” Read, the bratty, tomboy younger sister of the title character from PBS’ long-running animated series Arthur, has only ever been voiced by boys because young girls “were just too sweet” for the role, according to the show’s voice director.

Debra Toffan, who has worked as a voice director on the animated series since it debuted in 1996, explained the decision to cast young male voice actors in the part of the bossy but protective, unicorn-loving character while being interviewed for the latest episode of the newly launched Finding D.W. podcast.

“I’ve ...