Super Mario RPG is packed full of fun secrets. For many of them, you don’t need to get to the credits roll, but they’re simply so fun to do it’s hard to resist. The Temple Key in Monstro Town is one of them. So how do you get it?

Monstro Town is a place you visit late into the game. It’s an extremely unique location, as it’s full of monsters and built into a cliffside. The Temple Key is found above the second door to the right of the sign that reads “Welcome.” You will probably spot it pushing against the margin of the screen. It’s far too high to jump to, there are no nearby physical doors, and there are no footholds to get up there. It may seem like you need to drop down from above, but the actual solution is much closer at hand.
Go into the door below the key. There, you’ll find a home inhabited by a few monsters, one of which is a Thwomp. Talk to the Thwomp. It will open its statement by rising into the air before plunging down and shaking everything.
To get the key down, you need to talk to the Thwomp repeatedly (by my count, seven times) until the key above the door tumbles to the ground. They will start repeating, “Don’t you dig these vibes?” But that’s not a sign that the key has fallen. You’ll need to talk to them a few more times before the key falls. If you do it too many, it’s not going to make a difference. The key isn’t going anywhere. You can dig those vibes as much as you want.

What does the Temple Key do?
To use the Temple Key, you will need to double back to Land’s End. More specifically, you’ll have to return to the underground vault where you fought Belome. Before you actually reach his chamber, there’s a fortune statue of Belome’s head that will read a different fortune each time you hit it.
You want to get it to give the message, “Sorry, I’m not accepting visitors past my bedtime.” If that isn’t the message you get, you can back out of the room and try again. When that message turns up, get on the elevator, and you’ll be taken to a chamber. It’s blocked by a golden statue of Belome. Feed the key to the statue, and it will get out of your way. You’re then free to loot the chamber of some valuable treasures.
But to reiterate, to get the Temple Key in Monstro Town, you need to repeatedly talk to the Thwomp in the house beneath it to shake the key off the cliff.