When I first heard of Muppetzine when I first got the internet back in 1996, I thought it was an official Henson Company-produced/approved Muppet magazine. I didn't realize it was just made by fans with no involvement in the company (though official people did do interviews and correspond with the magazine). Just a few months early, I heard about things like copyright laws and needing permission to use other people's works, and assumed, though it didn't cross my mind at the time, that a fan could not legally make a magazine without permission from the company.
I probably should have thought the same about all the Muppet fan sites, but at first I thought the info on the internet was basically magic (ignoring things like mentions of web authors, times when they wrote as if the pages were done by individuals, notes from certain authors that they didn't know or have certain things, etc.), or that The Jim Henson Company was somehow behind all the fan sites in some way.
Even after I knew that websites were written by individuals and that many were not made or endorsed by Henson, I still assumed for a number of years that Muppetzine was an official Henson product.
I think I also thought Muppetzine could be found in stores with other magazines, even though I never saw any in person. I didn't realize that you had to order it.
And on a separate note (but it's something I first heard about at about the same time I heard of Muppetzine), I thought that Jim Henson: The Works was a book without many pictures. Just several pages of text and a few pages of black and white pictures in the middle of the book.