We were stuck in this room for a long time before we realized we had to throw the bucket down and jump on top of it. We actually had to come back and retry the game later, because we were stuck in this room for too long.
This one we eventually figured out, but it was a little hard to tell that you had to shoot a projectile up to break that door.
Playing through the game again, I think these are the only two outliers. Everything else was designed well enough so that you could discover how to proceed just by experimenting.