This happened to Hans somewhere around 2011 when he was abroad and went to a strip joint. He took a private dance and they went to a champagne room where the girl asked him what would he like. Being a simple man he said:

"Show me your ass"

But his English was heavy with his German accent and the girl heard him rather saying "Shove me your ass" so she decided to make sure

"Shove it? Shove it where?"

"Show it to my face" he replied

"Well alright" said the girl as she was relieving her ass from her mini skirt and panties

And that's how Hans learned of facesitting. When a random girl smashed her ass straight into his face. He's never been the same man afterwards