These are the various monsters found in Cave Story.

"Leaps and hops."
2 HP (hopping, blue and orange)
4 HP (hopping, green and aqua)
6 HP (hopping, red)
10 HP (hovering)
"Every cave needs a bat."
"For every cave a bat."

1 HP (blue and red)
2 HP (red energy and orange)
4 HP (black)
 The Door
"Possessed by something."

6 HP
"Charges when angered."
"Angry charger."

8 HP
"White mushroom."
2 HP
 Giant Pignon
"Worth eating."
12 HP
 Chinfish / The Egg Fish
"There's only one."
"Only one."

2 HP
"Slices you up."
20 HP
"Floor-hugging flash."
"Very Deadly."

"A model insect."
4 HP
"The big flyer."
15 HP
 Power Critter
"The crusher."
12 HP
"White mold ghost."
11 HP
"Tiny frog."
2 HP
"Big croaker."
10 HP
"Floats about."
4 HP
 Kulala / Kurara
"Queen Jelly."
50 HP
 Rabil / Ravil (Small)
"Violent Mimiga."
40 HP
 Rabil / Ravil (Large)
"Violent Mimiga."
300 HP
"Instant deathtrap."
32 HP
"Sudden chomper."
30 HP
"Wandering skull."
20 HP
"Sand runner."
20 HP
"White foe."
40 HP
"Sand Zone hunter."
20 HP
"Tough missile."
20 HP
"From one, many."
20 HP
"Scattering everywhere."
2 HP
"From Frenzied Toroko."
"Toroko's Flowercub."

1 HP
"Labyrinth dweller."
15 HP
"Labyrinth warrior."
15 HP
 Gaudi Egg
"Labyrinth baby."
11 HP
 Fire Whirrr / Fire Whirl
"Fiery fan."
50 HP
 BuyoBuyo Base
"Unknown organism."

61 HP
3 HP
"Gaudi spirit."
8 HP
 Fuzz Core
"Spirit clump."
10 HP
 Porcupine Fish
"An old friend."
3 HP
 Dragon Zombie
"Hatching failure."
"Failed hatch."

51 HP
 Counter Bomb / Time Bomb
"Timed explosive."

127 HP
 Night Spirit / Night Ghost
"Outer wall flutterer."
"In the Outer wall."

64 HP
10 HP
"Photosynthetic warrior."
"Photosynthetic foe."

16 HP
"Born of earth."
64 HP
"Stepping stone."
32 HP
"Mother bat."
64 HP
"Plantation dragonfly."
4 HP
"Hell's messenger."
4 HP
"Hell's messenger."
64 HP
 Green Devil
"Innocent demon."
2 HP
"Rolls along the walls."
2 HP
 Deleet / Delete
"Blocks passage."
31 HP
 Fish Missile
1 HP