Other stories result from a natural rivalry between two or more characters. Outside of performance, these are referred to as feuds. A feud can exist between any number of participants and can last for a few days up to multiple decades. The feud between Ric Flair and Ricky Steamboat lasted from the late 1970s into the early 1990s and allegedly spanned over two thousand matches (although most of those matches were mere dark matches). The career-spanning history between characters Mike Awesome and Masato Tanaka is another example of a long-running feud, as is the case of Stone Cold Steve Austin vs. Mr. McMahon, one of the most lucrative feuds in the World Wrestling Federation (WWF) during 1998 and 1999.