The paper airplane is hidden behind the TV; highlighting the nails was something I toyed with during the design phase but ultimately if they are always lit up then there was little reason to explore elsewhere. Once you get the advanced grappling hook upgrade you can hook shot onto any surface within range :)
I noticed far too late that it was possible to just get stuck in quite a few places, ideally I would have included some of the bounce-sponges within the drawers had time permitted.
There are some hidden coins up on the washing machine