Uncanny Eggs
Uncanny eggs is a simple little mod that allows players to craft a couple of eggs which when right clicked gives an average 45% change of being given a random spawn egg.
There are two varieties of egg, one that produces passive spawns called the Uncanny Egg and if this is combined with a spiders eye it becomes a Corrupted Egg and can then give hostile spawn eggs.
For pack devs the eggs are loot table based if you wish to change what spawn eggs can drop.