The Joker is one of DC's most chaotic characters by design, a villain who can become anyone or do anything — so long as it means making life difficult for Batman and the rest of DC's heroes. He's always resisted being a normal person in any real way, to the point that his worst nightmares seem to be a regular life. While that fits into the modern comics version of the character, it flies in the face of another notable Joker variant.
Source：https://www.cbr.com/joker-knight-terrors-family-nightmare-harley-quinn-dc-comics/
