After you get Santa's key, if you try and skip getting the fireball and somehow miraculously 'invici-jump' over Chaco's house -- she won't tell you about the fireplace passage unless you talk to Santa FIRST -- you'll have to go back to that area to get the charcoal and jellyfish juice.
Unfortunately, after fighting Balrog and talking to Malco, Santa will, instead of giving you the fireball, say " You're looking for charcoal. You can have what's in my fireplace." You can't GET the charcoal because you need jellyfish juice, but the jellies don't appear unless Chaco tells you about the jellies and her fireplace passage. However, she won't tell you unless you get the fireball, which at this point you can't, Santa being generous with the CHARCOAL now, and since you saved after the Balrog fight and therefore have to restart your game over again. Vicious cycle.
Yes, I tried it.