Animation Appreciation Thread #9

The Sakuga Wiki [JP] - http://www18.atwiki.jp/sakuga/
http://www.pelleas.net/aniTOP/

Other websites: http://pastebin.com/r2Vcy4b2

Animation on Twitter, Tumblr and Youtube:
http://pastebin.com/CQa8wU3q

Previous threads:
#1 http://dis.4chan.org/read/anime/1291816034 | #2 http://dis.4chan.org/read/anime/1314681601
#3 http://dis.4chan.org/read/anime/1325612276 | #4 http://dis.4chan.org/read/anime/1336754773
#5 http://dis.4chan.org/read/anime/1346337747 | #6 http://dis.4chan.org/read/anime/1349463339
#7 http://dis.4chan.org/read/anime/1350859696 | #8 http://dis.4chan.org/read/anime/1353020474

http://www.animenewsnetwork.co.uk/encyclopedia/anime.php?id=14940

What's the difference between main key animation and key animation? Also, why is a veteran like Takafumi Hori doing KA for an Animemirai short?