At u/PMmeifyourepooping's request, here's a standalone post with a link to one of my favorite "research" studies, courtesy of the group that gives out the Ig Nobels: "Postal Experiments," https://www.improbable.com/airchives/paperair/volume6/v6i4/postal-6-4.php.

While searching for the original article, I also found this followup article in the National Association of Letter Carriers' publication: https://www.nalc.org/news/the-postal-record/2011/april-2011/document/04-2011_strange.pdf. I love the first paragraph of the article!

Ask letter carriers about the strangest thing they’ve had to deliver on their routes and you’ll get some appropriately strange answers: adult-sized hula hoops, a broom (unwrapped), a desk chair (unboxed), a cowboy boot (unwrapped), a large homemade cookie with the address written in icing, and every conceivable kind of bug or small animal. Some carriers even deliver human remains and body parts. It seems like anything that can be shipped probably has been.