Everybody doesn't have huge buildings filled with big servers you know. Twitter is just finding it too hard to cope with all the small tweets everybody has to share all the time with the world.
The whale is so cute though. I'm sure they're going to fix it in due time but it's kinda relaxing to see internet giants finding problems sometimes too. Not in the way that I'm glad they're having problems. In a way that it's nice to know everybody's not perfect. ;)
P.S. It only does that for a couple of seconds then return back to its original state once you refresh the page after a while.