Was Quetzalcoatl a Viking?
Many of the Mayan peoples have historically worshipped a god called Votan, and many of them even changed the name of the third day of their week to Votan in honor of that god. Their records indicate that they learned of the worship of Votan from a people who came to the region on the Gulf Coast between the Yucatan Peninsula and the Isthmus of Tehuantepec from the island that we now call Cuba, and had come from even further north. A core of them actually settled in the northeastern portion of the Isthmus of Tehuantepec.
Furthermore, at least one Mayan temple has a mural (or at least had a mural — it's faded considerably since its discovery and is now invisible to the naked eye) dating back to around 1100 AD that depicts yellow-haired, light skinned men on longboats lined with decorated round shields and dragonhead prows fighting (and losing to) the Mayan population, which is depicted as dark-haired and -skinned. The appearance of the ships in this mural (I've seen facsimiles of it) is remarkably similar to the appearance of the Norman ships in the contemporary Bayeux Tapestry.
I definitely believe that Germanics reached what is now southern Mexico in fairly large numbers during the Viking Age, and I would not be surprised at all if worship of Quetzalcoatl began with contact between the American Indians and those Germanic visitors.