Cameos and References
This is a list of games and other media that have referenced Cave Story in some way or form. This page is still a work in progress and is by no means exhaustive.
1001 SpikesCurly can be unlocked as a playable character in 1001 Spikes by obtaining 30 golden skulls. She is equipped with a Booster 2.0 and her trademark machine gun.
The Binding of Isaac: Afterbirth+Quote and Balrog are two of the hundreds of randomly selected Co-op Babies. If you want to play as either you either need luck or a player 1 with the patience of a saint (since they have to wait while you dismiss and resummon your avatar over and over again).
Castle in the DarknessA statue of Balrog can be found in a room behind that ledge to the right of the fire bomb enemy in the Clock Tower. You will need the Wing Boots to reach it.
Creepy CastleBalrog can be found in Scenario 4 (Due Exaltation) within the Great Machine in a room accessible with the Lasso and the Jump Boots from Florius.
Crystal CrisisQuote and Curly Brace are both playable characters and the game's story is centered around the Red Crystal.
Umihara Kawase Fresh!Curly Brace can be unlocked as a playable character in the Switch and PS4 ports after completing quest 12 (Boss Battle: Giga Tadpole).
The Binding of Isaac: Four SoulsQuote, Balrog, Ballos as well as the Polar Star/Booster 2.0 are all cards in the Requiem Warp Zone set, which thus far has only been available to backers of the Four Souls Requiem Kickstarter.
BIT.TRIP Runner 2Quote is available as a playable character in the Good Friends Character Pack for BIT.TRIP Runner 2.
Cat PokePaintings of Quote and Curly can be found on the second floor if you can be distracted long enough from trying to poke cats.
DeltaruneIn Deltarune chapter 2 in the area to the right of the music shop you can see a red floppy disk with the same colour, lean, and spinning animation as the save point from Cave Story. It asks if you want to want to save, before realising that it didn't know what saving was.
DF CONNECTED (DONTFORGET)DF CONNECTED, the online-multiplayer spinoff of DONTFORGET (an Undertale fangame), has a variety of avatars available to players called vessels, and Quote can be unlocked as one.
Enter the GungeonThe Polaris, a reference to the Polar Star, can be unlocked by completing the Hollow 20 times.
Epic Battle Fantasy 3Curly appears as an NPC in this game and makes a passing reference to the opening hell narration from Cave Story.
Gang Garrison 2Press q on the character select screen to select either Quote or Curly as your character.
HexaneWhen Dell Talton is introduced in page 418 (in act 2) of the MSPA-style webcomic Hexane his room is initially depicted using pixel art in a similar art style to Cave Story, he has a Cave Story poster in the room and a Polar Star, both of which are later combined into other items.
Indie Game: The Movie: The GameIf you click on the SNES controller in the main menu of the Steam release of "Indie Game: The Movie" then you get an indie game character mix and match game.
I Wanna Kill the GuyCurly is used as an optional dance off boss in chapter 3 of IWKTG v.052.
Kid Icarus: UprisingUnverified possible reference from the opening lines of the Powers tutorial:
"Remember, Pit, you won't be fighting alone out there."
"You're going to send me a machine-gun-robot girlfriend?"