The Ländler (dance)
Much flail. So blush. Many squee. Wow.
Okay, doge meme aside, this is the first scene that we see Maria and Georg really interacting more like a couple. Before this scene opens, Maria had been trying to teach Kurt how to dance the ländler, a traditional Austrian folk dance from the 18th-19th century. Then Daddy Georg steps in and is like "Lemme show ya how it's done, son." xD
This scene is also highly symbolic--the dance symbolizes the sexual tension growing between Maria and Georg. Close to the end of the video we see Maria step away from him, blushing madly, saying "I don't remember any more" (of the dance), subtly hinting at her inexperience and virginity.