Hardcore Superman fans know that Luthor originally had a flowing mane of red hair.
He looked more like Mickey Rooney as the Joker than anything else.
The unintentional change is a lesson in trying to do too much. After debuting in Action Comics in 1938, Superman quickly became the most popular comic book character ever created. In a matter of years, there were Superman graphic novels, spinoffs, and newspaper dailies. Creators Jerry Siegel and Joe Shuster couldn't keep up with the trend, and soon started employing ghost artists -- illustrators who could mimic Shuster's style while Shuster still got the byline. Because of the massive turnover, these artists often worked with little preparation and strict deadlines. Superman's newspaper ghost artist, Leo Nowak, had the difficult task of drawing Superman comics on a daily basis, and did so by quickly reading the script Siegel sent him. Unfortunately, when Luthor popped up again, Siegel's script didn't mention anything about his sinister red locks.
The story goes that when Nowak went through back issues to see what Luthor looked like, he mistook another bad guy as the manipulative millionaire (specifically, one of Luthor's henchmen, a stocky bald guy who did most of the villainous work in that particular issue).
He was this close to giving Lex a TV for a head instead.
Before anyone noticed his mistake, Siegel and Shuster invited Nowak to ghost draw Superman #10, in which Luthor also appeared. So of course, Nowak once again drew Luthor as a broad-shouldered cue ball, rather than the tiny, purple-suited ginger he had been in his original appearance. When Nowak presented his work to the creators, Shuster liked the bald version of Lex better -- a decision which surely had nothing to do with the fact that Shuster had a habit of drawing hair like a mold of shiny plastic melted atop his characters' heads. Over the years, Lex's hair loss has become official D.C. Comics canon, despite the fact that it was really a product of overworked cartoonists.
"I just lost all of my hair! Save yourself before the radiation consumes you too!"