Goblin eggs
or any eggs in general
Viewing post in How do I get rid of the eggs in Hiro's belly?
IIRC to remove the goblin egg you need to fertilize it(I think the werewolf, centaur and harpy can fertilize it), and you need to wait sometime for it to develop and hatch, for the mermaid one you just need to wait sometime and when the egg is ready to hatch, you will need to go to an body of water or river(can't remember wich one), for them to hatch.