Sims 4: I have two mailboxes and a unicorn that I can't remove

Here's your reply (although you probably won't like it):

Others have this issue with the mail box and I have not found anyone who knows how to delete the extra mail box (this is also a problem if you turn an residental lot into a commercial one. The mail box also gets stuck)

As for the unicorn, the game MIGHT clean that up by itself. It does clean up stuff from time to time but I kinda doubt it recognizes the unicorn as a object that needs deleting so you're probably stuck with it.

I can offer you two solutions

• If you have, go back to a backup where this hasnt' happened. The game makes automatic backups and you can try if any of those don't have the issue: http://sims4.crinrict.com/en/2014/09/save-games/#wiederherstellen
• Live with it.