I recall that our late friend Mary LaMarca penned a beautiful opus about the Ring Cycle, to the tune of "Barret's Privateers," that was a wonder, plus having all the main plot points from the bloody story!
I did a quick search, and can't find it, alas. It'd be a good addition to the DT, says I. Ditto her contribution to a 2000-election shanty by the Civil Serpents, "AN ELECTION SHANTY," which is in the DT.
And Joe Hickerson's not-quite-complete parody of "The Christmas Song" goes:
Christians roasting on an open fire,
Lions nipping at their toes.
Pagan carols being sung by a choir,
While Romans raffle off their clothes, everybody knows
When Nero played his violin,
Ancient Rome was all a-glow.
One dead Jew, or an Arab or two,
Hari Krishna to you.
As you see, it misses the bridge part of the original.