Where did Anakin get his scar?

So how did Anakin Skywalker get his noticeable scar during Revenge of the Sith? Most of us who watched the Clone Wars mini-series when George Lucas was asked about it his response was “I don’t know. Ask Howard,” says George, referring to President of Lucas Licensing Howard Roffman. “That’s one of those things that happens in the novels between the movies. I just put it there. He has to explain how it got there.{C}{C} I think Anakin got it slipping in the bathtub, but of course, he’s not going to tell anybody that.” this is according to the article “How did Anakin get his Scar?” by Amelia Hill from about.com.  She goes on to talk about the “orgins of the scar” and the “canonical problems” that are present.