Okay, I guess I have a very bad case of brain freeze because I don’t get the joke. The nursery rhyme song’s lyrics don’t trigger any kind of punch line for me. The lyrics are:
Three blind mice,Three blind miceSee how they run,See how they run!
They all ran afterThe farmer’s wifeShe cut off their tailsWith a carving knifeDid you ever seeSuch a sight in your lifeAs three blind mice?