I don't know how I missed the reference, but in Lewis's 2nd Chronicle of Narnia, Prince Caspian, the valiant mouse Reepicheep loses his tail in the Second Battle of Beruna and believes this is a severe humiliation for a mouse. His followers are so devoted to him that they are determined to cut off their own tails rather than exceed their leader in honor. This display of affection so moves Aslan that he relents and restores Reepicheep's tail, despite his worry that it will encourage pridefulness.
This is an echo of the Knights of the Round Table after Gawain's return from his adventure with the Green Knight. Because Gawain did not show entire honesty in his dealings with the knight, disguising that he had received a green sash from his wife on the third day of temptation, the greatest of Arthur's knights (for so he was until the French go ahold of the story) deeply feels the humiliation of this and vows to wear the sash as a mark of his dishonor until the end of his days. The other knights regard his honor and piety as far exceeding that of other men, however. He did refrain from having sex with a magical temptress for three successive days, after all, slipping only in the final moment by accepting a gift from her and not telling her husband about it. They thought this was a pretty good innings, and resolved to wear a green sash for the rest of their days as well.
We still see this from time to time these days, when the boys in an elementary school class will all get their heads shaved in solidarity with a classmate who is undergoing chemo and has lost all his hair. I tear up whenever I read about such things.
Resisting sexual temptation seems to be one of the top few signs of piety in the Arthurian tales as they have come down to us. As this does not figure prominently in the earliest stories of him, we can again blame the French for their excessive sexual focus once again. OTOH, it might be fairer to give them credit for saying aloud what was likely well-known to the Welsh, Britons, and Bretons beforehand but not mentioned. Monty Python was not the first to highlight this temptation. They were drawing on a well-established tradition. Heck, even I made reference to it in my Arthurian opera in 1971, before the movie came out.
Parody usually cuts to the heart, even when inverting the point. They certainly did here.