I tried to look around to identify them, but i dont really understand who they are supposed to be...this is their pixiv tag: http://www.pixiv.net/tags.php?tag=%E3%81%B2%E3%81%93%E3%81%AB%E3%82%83%E3%82%93
the names are 'Sento-kun' and 'Hiko-nyan', if anyone want to give a try and search around.

Come on, Japan. Where are all the pictures of Sento-kun cosplaying as Santa's reindeer?