In an early release of Viggo on Glass, the level would be impossible to complete due to one of the Oxygen Bottles floating above the player's jumping range. This was fixed in a later update.
In the Dreamcast and PS2 version, you can climb up one of the trees in the raining dome. For the former, you must jump into the first tree you enter at the side facing the door and hold down the forward button, and for the latter, you must jump into the shortest tree from the walkway and hold down the forward button. Stay on that side and you will slowly move upward until you reach the top. If you are playing as Tweek, gliding will cause him to fall down. There is nothing much of interest at the top, except you can get on top of the other trees (although in the PS2 version, you have to play as Bungalow to reach them), and the top area lacks rain.