First, if you hit the bucket at the beginning and then go into PD 0, when you come back out it will be impossible to go through the secret passage, but you can enter level 1.
Second, If a frozen bobble is falling down against a wall, it can unfreeze and begin to move along the wall.
As a side note the coin on level 0 can only be gotten once, either before or after PD 0.
