Explanation

1. If this option is enabled, there is a certain chance of charged creepers spawning instead of normal creepers.
2. Also, there should be a certain chance of "Toast"s and Killer rabbits spawning instead of normal rabbits.

Why?

1. The only way of getting charged creepers is by hitting them with lightning, which is a tedious task since there are no tridents in 1.12. Besides that, it would make a great addition for making the game harder.
2. There is no way of getting Killer rabbits in survival minecraft.

Additional information

This has been implemented in a similar way by PurpurMC.

https://github.com/PurpurMC/Purpur/blob/ver/1.19.3/patches/server/0028-Charged-creeper-naturally-spawn.patch

https://github.com/PurpurMC/Purpur/blob/ver/1.19.3/patches/server/0029-Rabbit-naturally-spawn-toast-and-killer.patch