(CNN) A Michigan woman got the Secret Santa gift of a lifetime this Christmas -- an 81-pound package from Bill Gates.

The gifts included an original manuscript of "The Great Gatsby," signed by Gates; books; toys for her cat and Harry Potter and "Twin Peaks" memorabilia, according to her post on RedditGifts.com. It arrived in a box lit up inside by Christmas lights.

Shelby, who asked that her last name not be shared, received the gift through annual Secret Santa exchange on RedditGifts, which hosts dozens of themed exchanges each year. The site is run by Reddit, which runs the popular discussion site by the same name.

"It's well documented that Bill Gates has been participating for years, but I never, ever thought he would be my Secret Santa," Shelby said. "It's really surprising."

A spokesperson for Reddit confirmed that Gates sent the package. The billionaire has participated in the exchange since 2013.

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