There is a school of thought that says that this annoying ad is based on the song
"The court of King Caractacus" by none other than Rolf Harris... (check out YouTube for some interesting renditions... especially Tony Robinson going crazy on Play Away)
Some think that it is based more on the poem "Night Mail" by W.H Auden
This is the Night Mail crossing the border,
Bringing the cheque and the postal order,
Letters for the rich, letters for the poor,
The shop at the corner and the girl next door.
Pulling up Beattock, a steady climb:
The gradient's against her, but she's on time.
Jim Bolton, the creative director at Leo Burnett, the ad agency that produced the McDonald's advert, says : "It's actually based on Rolf Harris's song, Court Of King Caratacus. He gave us permission to use it, and then two of our copywriters changed the lyrics." That's poetic licence for you.