If a parody is sung at a Folk gathering where the audience are regular, and know each other, it often spells the end of that particular song in its original format. The parody will be remembered and discussed each time the song is sung. If the song has become too frequent, and people are fed up with it, this is fine, but more often than not it is the favourite song of one or more of the participants, and their enjoyment of it is partly spoilt, as a result.
Malcolm has, certainly, done this to a few songs, but he is a particularly clever exponent of the art, and one of the few who can break through my humour barrier.