Why did Michael Richards refuse to portray himself?

In the 1999 film "Man on the Moon" starring Jim Carrey as the infamous comic Andy Kaufman, the movie takes great pains to recreate specific points in Kaufman's life. In a somewhat unorthodox fashion, however, many of the original actors/actresses that Andy crossed paths with were called back to assist with the re-creation of those very same scenes.

So, aside from the obvious amount of time that has passed (the actors and actresses clearly all look a bit older) the scenes are more-or-less exact replicas of what happened in Andy's past. This includes many cameos from the cast of Taxi, wrestler Jerry Lawler, SNL Producer Lorne Michaels, David Letterman and more. There are most certainly some actors that weren't able to reprise their roles, for various reasons (the scene wasn't important enough, the original actor wasn't available/dead/etc), but there was one key actor missing who could have reprised his role--for a very significant scene: Michael Richards, in the "Friday's" incident.

Back in '81, Andy appeared on a live sketch comedy show which attempted to take advantage of the success of Saturday Night Live. It was comprised of young comedians getting their start in the industry, and performing sketches on live TV, much in the same fashion as SNL. On one particular night, a sketch involving four friends (one of which was played by Andy Kaufman, another by Michael Richards) took place at a restaurant, with the joke being that they would get up at various times and head to the bathroom to smoke marijuana. About half-way through this sketch, Kaufman decided for whatever reason to go off script, infuriating and frustrating his fellow cast members. At one point, Richards goes off camera and returns with the sketch's cue cards, and tosses them on the table in front of Kaufman, at which point Kaufman sprays Richards with a glass of water, causing even more friction, and an eventual fight breaks out between Kaufman and Friday's co-producer Jack Burns.

Andy was known for unconventional humor. Throughout his career, he made a lot of judgment calls about what he thought was true comedy, but that not very many other people seemed to agree on. One recurring theme in his comedy was that he liked to keep the audience guessing. Was what we were seeing really real? Or was it all an elaborate hoax? A staged event that really truly seems like it is actually happening, only to find out later that it was a sham from the start.

Many people that Kaufman staged these "events" with now confirm today that they were, in fact, staged; the most famous of which could be considered the entire series of events that took place between wrestler Jerry Lawler and Kaufman. And, as expected, in the case of the "Friday's" incident, it was also revealed later that the entire scene...Kaufman going off script, Richards' frustration, the cue-cards, the water splashing and eventual fight...all was a plan from the beginning. Richards himself confirms this in an episode of "Speaking Freely" (Video).

Even though people confirm that these Kaufman-events were planned from the start, one very real fact remains: out of all of the actors/actresses that ever had the luxury of coming into contact and dealing with Kaufman, and were given the opportunity to return and pay homage to Andy by recreating those same scenes in the "Man on the Moon" film, one person refused: Michael Richards.

The question is, why?

If, like so many other actors, Richards had truly been "in" on the event from the start, then shouldn't he, as a comedian, understand the value of that comedic genius and want to pay homage to it like others? Or was there another reason that kept Richards from participating, other than the most basic guesses of "it was an embarrassment for him", or "he simply didn't want to re-live the past", or even "his schedule simply didn't allow for him to contribute to the movie" (which seems unlikely).

Is there any proof available to the story that the event, though portrayed after the fact as a hoax, may have truly been, in fact, something that Kaufman came up with on-the-fly, and the network/people involved simply used "oh, it was planned" as a cover for them losing control of Kaufman on live TV--and that the real reason Richards refused to portray himself in that infamous scene was due to the fact that he knew the truth...that Kaufman embarrassed Richards and his fellow cast members on live TV without their knowledge, and to this day, will really have nothing to do with any homage paying tribute to Kaufman?