How about the best fail that wasn't really a fail. In the early eighties, Friday's was ABC's attempt to ride the SNL wave. On Feb 20, 1981, this aired on live TV.
[video=youtube;bN5vhvIAqY8]http://www.youtube.com/watch?v=bN5vhvIAqY8[/video]
The fight was staged. Only a few people were in on it, including Michael Richards and, of course, Andy Kaufman. The joke was not revealed at first. Instead, Kaufman returned the following week to issue an apology and whine about how the incident had ruined his life.