Cave Story 100% requirements

Changelog:
2019-06-18: Rewritten version rules for consistency with the speedrun.com CS+ 100% leaderboards.
2019-02-19: Rewritten "All collectibles" definition to allow using collectibles that can be used (such as Life Pots)
2019-02-15: Redefined "All Weapon Slots" requirement to allow Snake as a possible weapon. Improved definition to allow Cave Story 3D 100%.
2018-04-27: Added Little Man Sidequest as a requirement.

Version considerations:

All official versions of Cave Story can run 100%. However, each version group (Original, Steam/WiiWare/DSi/3ds eShop, 3D, Switch) keeps separate leaderboards due to version differences.
Runs can be performed on Easy or Original difficulty, with each difficulty running in separate leaderboards.
Runs can be performed in Curly Story (and compete against Original difficulty) but it's not recommended due to more text making them slower.
It is not required to obtain Beast Fang when running on Cave Story 3D.

->All Life Capsules

Run must collect all Life Capsules, and finish having a max HP of 55 (or 98 for Cave Story 3D). All life capsule locations can be found here: http://cavestory.wikia.com/wiki/Life_Capsule

->All missile expansions

Run must collect all available missile launcher expansions, and finish with 54 max missiles. While it is possible to end the run with 100 missiles, it requires to ignore all missile expansions but the last one, which goes against the spirit of a 100% run. More information in http://cavestory.wikia.com/wiki/Missile_Launcher

Please do note that both rules mentioned above imply the run must beat Best Ending, since one Life Capsule and one missile expansion are located within Sanctuary.

->All 5 weapon slots

Run must obtain all weapons that fill a new weapon slot (Polar Star, Missile Launcher, Fireball, Blade, Bubbler). It's not required to acquire all possible weapons, just to get all 5 slots used. As such, Nemesis is not required for 100%, but Bubbler is.

Run must also acquire one of the Polar Star upgrades (Machine Gun, Snake or Spur). Current optimal route ends with Machine Gun/Super Missiles/Fireball/Blade/Bubbler.
Run also requires to get Super Missiles.

-> Complete the Little Man Sidequest

Little Man must be collected and then returned home. It suffices to leave him home, and it is not required to obtain Nemesis from this sidequest.

->All possible collectibles.

Run must collect as many collectible items (as in, items displayed in inventory) as possible given the aforementioned rules. Current collectible item list in route is
-Silver Locket
-Map System
.Arthur's Key
-ID Card
-Chako's Lipstick
-Rusty Key
-Gum Key
-Curly's Panties (most important item in the run)
-TurboCharge/Whimsical Star (if applicable given your Polar Star upgrade)
-Clinic Key
-Arms Barrier
-Tow Rope
-Curly's Air Tank
-Alien Medal
-Booster 2.0
-290 Counter
-Teleporter Room Key
-Sue's Letter
-Mushroom Badge
-Iron Bond
-Medal of the Red Ogre