At the 1978 Science Fiction Film Awards, William Shatner provided one of the most unique covers of a pop song, certainly in a sci-fi convention, but maybe at any convention, or anywhere.
Over the years, Shatner has weirdly denied it happened, but it did, and Flemishdog found a U-MATIC videotape with an unaltered, high-quality version of Shatner's "Rocket Man". And here it is.