Huh. I feel disappointed in myself for not making that connection earlier. 
Then again, besides the little head-mane thing, it doesn't look that much like an Arceus. So I guess the better question (for my benefit since I have no clue) is 'how did Arceus transform into this thing?' 
Is there actually an answer out there or is it secret? 
EDIT: Oh, and no, I didn't.