Expected behaviour:
Right clicking a mob with the corresponding Spawn Egg would produce its baby version.
Actual behaviour:
Right clicking a mob with the corresponding Spawn Egg does nothing.
To reproduce:
Open a creative world, get the Spawn Egg of any mob with a baby version and right click the mob with the egg.
Duplicate of MC-86142. If you have not, please search before reporting issues to see if your issue has been reported already.