Textures: All mobs are children [1.21+]

Textures All Mobs Are Babies do exactly what their name says: all mobs will become little children. Moreover, changes will get even those creatures in Minecraft, which do not have child variants. Naturally, it is worth remembering that this is only a set of resources - the mobs themselves will receive only a model update, but the behavior will remain the same.

It is worth considering that the hitboxes of mobs will remain the same, so small mobs will have a high hitbox.