If you are following William Shatner's tribute to Leonard Nimoy on Twitter today, you've seen some references to Nimoy's bike and what Shatner did to it while working together on Star Trek. Though it is mentioned a few times, the story behind the bike is not given other than assuming we all knew it. I did not so I looked it up. The below video is of Nimoy and Shatner telling the story of the bike and it's a great video about how these two played off of each other.
The video doesn't list where or when this is from… but it's too good to not link it.