The firehouse hides an apartment. Much like in the real Disneyland. It can only be opened during the Blot Apocalypse.
Everyone in Wasteland is the size of an action figure. Which is why all the merchandise in Mickey Junk Mountain is so jumbo in size.
According to the novelization of the original game, the reason Yen Sid didn't fix Wasteland was because he wanted Mickey to correct his own mistake. Over 80 years between the Blot creation leading to the Thinner Disaster and the events of the game just make him look too lazy to care.
The Blot now has glowing purple light in its black ink.
Oswald may be innovative and caring for the forgotten toons, but he is ego can get the better of him. He stupidly started doing a "fight me" prance on the cork holding the Blot in the bottle: shortly after Mickey admits he created the Blot and caused the Thinner Disaster by ACCIDENT. It's more of a surprise there isn't a subtitle for Oswald saying "I'm such an idiot"