I THINK this might be the greatest one-off performance of a song.
To give it some context for those who don't know, The DKs were invited to play the Bay Area music awards in early 1980, to give the event some 'new wave credibility'. They were expected to play California Uber Alles in front of the assembled music industry vips. However, a few "seconds into it, the band stopped and Jello Biafra exclaimed:
"Hold it! We've gotta prove that we're adults now. We're not a punk rock band, we're a new wave band"
They then launched into 'pull my strings', an attack on the music industry (sample lyrics: "is my cock big enough, is my brain small enough? For you.. to make me... a star?')the knack (referencing 'my sharona' which they changed to 'my payola') and even Bob Hope.
When, towards the end, it's sung briefly the style of Bob Dylan, it's so perfect that it makes me want to cry.
The Dead Kennedy's were never invited back. The song was never performed again or recorded in the studio, but can be found on the compilation 'give me convenience or give me death'
I vote this the greatest one-off performance of a song in music history.
Any other contenders?