@RR529
First, did you talk to Prof. Booster when he fell from the ceiling? If you ignored him, then did you save Curly/Quote after the Core fight? If you did either, then you won't be able to open the chest. As for the Nemesis, you must find Mr. Little (who is walking around the lower level of the Mimiga Cemetery) and return him to his family. He will then offer to trade the Nemesis in exchange for the Blade. Ask me if you have anymore questions. I love answering questions!
EDIT: Ninja'd.

@Anyone Did anyone try curly's story before the patch? It was something right out of a creepypasta! D:

@HappyMask
Unfortunately, I must have bought the game after the patch as I found nothing weird about it. What happened before the patch?

You fall through the floor of the beginning Kazuma cutscene, All the textures are all over the place, and you drown at the first second you start. D:

That... that is creepy. O_O

I got the Nemesis. Thanks to everyone for the tips

Finally unlocked the last song! With my no doubt record breaking boss rush time of 28 minutes. WOO I AM THE KING

Also, Nemesis Challenge is insane! I thought you just had to make it through that first room...Lord knows that took me long enough. Then finally I do that and...another room! Cave Story hates me.

...but I love it so much.

Ha! My record is 17'08, according to the game.

For some reason, my Quote has dark blue clothes & red eyes for some reason (that sprite isn't for Easy, Normal, or Hard difficulty).

Does anyone know what's up?

EDIT: The same strange pallet has also affected my Curly (in Curly Story). Is it some sort of glitch?

@RR529
Nicalis released an update for the PC version of Cave Story+ to coincide with Halloween, so maybe that has something to do with that.

Its Halloween
CaveStory on DSiware and Wiiware did the same, and If your wearing the Miniga, it will look like your wearing a Jack-o-lantern

Oh, that's pretty cool. :3

Just picked up where I left off in "Curly Story". Just beat the boss in the Labyrinth (the robot that moves back & forth on the tracks).

I forgot just how epic the game's bosses are, lol. It took me a couple tries, because I'm a bit rusty, but I got through it.

Guys, apparently there is a fourth ending to Cave Story. In this ending, two certain key characters survive, some certain events are changed, and even a few battles are skipped. Check the video on how this ending can be achieved:

Hi, I hope this question doesn't sound stupid. I searched for the DSiWare version of Cave Story on the Nintendo eShop and couldn't find it, but did find the 3DS version. Does that mean if I transfer Cave Story from my DSi to my 3DS XL it will become the 3DS version, or will it stay the DSi version with the DSi resolution?

It will stay the DSi version.

Thanks for the reply! And darn!

Well, you can only play Cave Story so many different times on so many consoles. XD
There seriously needs to be a full-blown official sequel to this game.