It was obvious as soon as the new season of the Hetalia anime had started showing, because Nico Nico Douga was suddenly full of brand new videos based on the series almost overnight.
This first one cracked me up when I saw it. It's an western-style movie trailer for 'Nekomimi Ninja', which seems to be some kind of imaginary crime thriller starring Japan. It's notable for starring a huge number of Hetalia characters, and more importantly, for featuring instantly-iconic synthesised dialogue straight out of a machine translator. Thank you to user yusura for making me laugh out loud.
The second is a beautiful dance by male and female versions of Japan set to Sasa No Ha Sarara by user Kairi. The ornate costumes give a glimpse of the charm of Japanese history.
Sengoku Basara video community is still going strong. Here ku-ya puts six of the boys in their Gakuen Basara attire to dance to Kagamine Len's inappropriately lewd song, Gigantic O.T.N.