Java Edition:Size Potions
In the April Fools' version 23w13a_or_b, two new potion types were added called "Big Potion" and "Small Potion", these either increase or decrease an entities size when applied. They must be enabled by approving the votes minecraft:potions_of_big and minecraft:potions_of_small, respectively. They are converted into their no NBT equivalents when updated to 24w09a (a 1.20.5 snapshot) or newer.
Obtaining
in 23w13a_or_b the "Big Potion" can be made by approving the minecraft:potions_of_big vote and brewing an awkward potion with a bottle o' enchanting in a brewing stand. The "Small Potion" can be made by approving the minecraft:potions_of_small vote and brewing an awkward potion with a rabbit hide in a brewing stand. Updating these potions will not show the potion effect and will not apply the effect if used, but the NBT data will be preserved.
Observability
This feature is directly observable in 23w13a_or_b, but outside of 23w13a_or_b these potion types are indirectly observable. Potions with these effects can be differentiated from uncraftable potions due to having additional NBT tags that are not present on uncraftable potions.
Variants
There are 12 variants of Big Potions and Small Potions, these include the Potion of Big/Small, Splash Potion of Big/Small, Lingering Potion of Big/Small, and Arrow of Big/Small. Additionally, each potion can have the duration extended with redstone, or have the level increased with glowstone.
All 12 variants of the Big Potion.
A wall of Small Potion items.
All 12 variants of the Small Potion.