Spoiler for ep5 references, not extremely plot related:
So far interesting references I've noticed...
Gaap steals some items from Beato... the Silver Crystal and Moonstick
「幻の銀水晶とムーンスティック返せ－！」
and, is Rudolph singing what I think he's singing?
♪俺はぁ、イナ・バウア～、常に大ピンチ～…っとくらぁ。」
I'll probably come back and edit this post when I recognize more (I'm sure there will be much more... )