Slimes

Slimes are the most common enemy type. They are almost always the first enemy the player encounters in a new world. They come in multiple sizes and colors, each with different health and damage. All slimes follow basic Slime AI and attack by hopping onto the player (with the exception of the Gastropod). When a slime is preparing to hop, it bobs up and down rapidly. Slimes can float in water.

Slimes spawned on or near the surface are usually neutral and do not chase the player during the day, unless provoked. They become hostile at night. Slimes spawned underground are always hostile. Green, Blue, Red, Purple and Yellow Slimes usually spawn on or near the surface. Mother Slime, Baby Slime, and Black Slime can only be found underground. Pinky may appear anywhere, yet rarely.

Most types drop 1-2 gel, but there are numerous exceptions.
 * Corrupt Slimes and Crimslimes drop 2-4 gel.
 * Lava Slimes and Dungeon Slimes drop no gel.
 * King Slime drops no gel, but the Blue Slimes it spawns can produce a large amount of gel.
 * Pinky drops 25-50 Pink Gel.
 * Rainbow Slimes drop 1-20 gel.
 * Gastropods drop 5-10 gel.
 * Umbrella Slimes drop 2-5 gel.

Gel is a vital ingredient, as it crafts Torches, which are of use throughout all stages of the game. Pink Gel is less necessary, however allows for the crafting of powerful early game tools and the Peace Candle.

Bonus drops
Naturally spawned slimes that have the same shape as a Blue Slime have a 5% (1/20) chance of carrying a bonus item.

Slimes spawned from statues can never carry a bonus drop, and Dungeon Slimes will always have a Golden Key as a bonus drop.

Trivia

 * Slimes are hinted to be made of a digestive substance by the Nurse in her dialogue: "You look half digested. Have you been chasing slimes again?"

History
Schleime Slime Slime Slime Слизень 史莱姆