Mystery solved.
It wasn't an elf at all, but a father and son team who live on a boat in San Francisco Bay.
Tony Powell and his six-year-old son Rio have taken credit for creating the whimsical tiny front door affixed to a tree in Golden Gate Park, according to the RichmondSF blog.
Tony is a skilled craftsman with the chops necessary to shape and carve wood, the blog reported.
He told the reporter the inspiration for the door came from the ages.
"Of course people have given recognition to the creative spirits of nature for ages. The Greeks called them by such names as Dryads (tree spirits) and Naiads (spirits of stream and lake), and the Irish called them the Sidhe (pronounced 'shee,' as in banshee)," Tony explained.
He said he and his son installed the door around Valentine's Day, after which time the door became an international media darling. Because they live on a boat, they did not see the media coverage.
Media from Europe reported about the mystical wonder the door created for visitors, who flocked to the elm tree and left notes and flowers inside.
The door's creators said they were touched by the offerings people left inside the door. Tony said he even answered one of the questions left on a note left inside the door.
"One of the notes asked whether fairies were real. I had to scrawl upon it in green crayon, 'Yes we are,'" he said.
The city's Recreation and Park Department got wind of the door and removed it — only to replace it with a second door soon after. The door will have to go permanently, as fixtures to trees like hinges cause damage, according to park officials.
But in the meantime, Tony and Rio are enjoying the magic they've created in what is a magical place to them — and many other people.
Photo Credit: Joe Rosato Jr.