Amy was intended to be the engineer character in the show's early development. After casting the more feminine Tom, they revamped her character to better fit her comic persona.
Speaking to People Magazine, Tom recounted that "the concept for Amy, originally, was that she was supposed to be kind of a very tough, sort of butch car mechanic."
She continued, "I'm not, that's not really my persona that I put out, you know, so when I met Matt [Groening] he's like, 'Huh, well, we'll have to figure this out.'"
Tom then explained that the character was changed to be softer. The role of the tough one went to Katey Sagal's Leela, with Tom adding that it "fit perfectly with her persona."