Tried to do that also and got these screenshots:
Trash appears in the rooms just randomly from version 0.6.3
I knew that there was an entity that walks randomly in the pools behind the player, but I never noticed these entities, I throught that it was just the light flashing for no reason.
Also, the tutorial hints disappear behind it, so it is definitely an entity and not a visual effect:
(1 frame after it disappeared)