I learnt an interesting fact today that I have never heard before.
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Getting into the Xmas spirit I read a Rolling Stone interview with the Director and cast of National Lampoons Christmas Vacation.
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He says the title song “Christmas Vacation” performed by Mavis Staples and was produced by none other than our Prince!

Quote below:
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Chechik: I always wanted the animated opening you see in the film, but Warners balked at the cost of doing an animated title. So rather than get into a fight, I designed another title sequence with a Christmas song sung by a Jamaican who sounded like he had no teeth and you can barely understand the words. Then the replacement title sequence looked like an old French art film, with white titles on black. When I proposed this to Warner they said, "We think the animated titles are great." For the theme song, Prince was a Warner artist and he produced it. He's the one who brought in Darlene Love.