WHOSE birthday?!?

I chanced upon a couple of odd photos over on Twitter during the week -- birthday drawings of Mr Crepsley! I'm not quite sure if this is a random thing -- if one fan decided to do a fun birthday themed drawing, which was seen by another fan who then did their own version -- or if this is a Shandom thing, i.e. if a group of fans came together and chose a certain date in April as the grumpy vampire's day of birth. If anyone can enlighten me, please do. But regardless of any of that, they're a c...