"Joker.rar" does not refer to a single, famous mystery or malware entity. Instead, it is a common filename used for various fan-made digital assets related to the DC Comics character, the Joker, and other characters with the same name.
: Ensure you are downloading from a reputable modding community or official creator page. Jeff "Joker" Moreau [Mass Effect] - SFMLab Joker.rar
: Fans have created highly detailed skins and clothing sets to make characters look like Heath Ledger's or Jack Nicholson's Joker. These are often shared on community forums like Insimenator as "The Joker.rar". "Joker