Do not offend the organist says an article in The Telegraph:
...if new research is be believed, behind the quiet exterior the humble church organist is not someone to be crossed.
While charged with providing spiritually uplifting music to worshippers, it seems many also seize the opportunity to extract subtle revenge on clerics who have displeased them or simply play pranks on congregations.
Among examples cites was that of the organist in Scotland who had fallen out with some of the elders in the Kirk but got his own back by inserting a thinly disguised rendition of “Send in the Clowns” as they processed in for a Sunday service ... In one decidedly high church congregation, an organist punctured the mood of reverence as an elaborately dressed clergyman processed back after the gospel reading – by playing the theme tune to The Simpsons.