Polar opposite

Norman called up his only friend Walter with a snort. He was excited; the two nerds often showed off new inventions to each other, and this time Norman had a big one. As he explained to Walter, the device could actually fuse two people into one. Walter immediately volunteered for the sake of science! But with Norman having to operate the controls, they’d need another person. The pair didn’t really have any other friends. The two thought for a moment, but the doorbell interrupted them. Norman had been so excited about his device that he had forgotten that his sister Bella was coming to visit. She’d be perfect! She was the polar opposite of the nerds -- pretty, popular, and a little on the dumb side. It wasn’t hard to trick his simple-minded sister into the experiment. It wasn’t long before Norman had merged Walter and Bella into one person. The device had snatched an X chromosome from Bella and an X from Walter -- making the fusion female, but Norman was really curious about this fused person’s personality!