I hate to tell you that it wasn't a joke. It's all explained in this month's issue of SI, where they did a "Where are they now?" piece.
Ends up it wasn't a joke, and SI bent to public criticism by saying it was a joke. Plimpton ended up leaving the magazine over their lack of journalistic integrity in the matter.
I suggest that you read the article in SI ("Refridgerator Perry" on the cover), because apparently, this guy has been practicing the javelin in secret and could possibly be in training for the Olympics in Sydney.
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I am Jack's raging inner child. Without me, Jack has to deal with the pitfalls of reality.