This mod allows you to add custom critters to the world.
See eemie's Bees for an example.
Wed, 09 Aug 2017 16:26:55 -0400
Full ChangelogFixed not spawning critters if the vanilla critter cap was reached.
Fixed only being able to select positions in tile increments.
Fixed chances being inverted for spawn choosing.
The source code for this project can be found here.