You've all been searching for it! Or at least google says you have, and so have I! And I found the answer!

So here it is! The commands to REMOVE or ADD your pets irrational fears and obsessions of random objects! Or even better? Wish your dog was loud? Wish it was quiet? Wish your pregnant cat didn't throw up everywhere? Wish it slept in an adorable little ball instead of on its back? HERE YA GO! Just keep reading!

In order to do this you need to open up your cheat bar (CTRL + SHIFT + C) and write "testingcheats on". After writing that it should say something like "Cheats enabled." When it has said that, just start typing in the commands!

Note that successfully doing these commands will require you to have your pets selected, the Playable Pets Mod may be needed for this.
In order to figure out what traits your pets have, and also whether or not your command was typed correctly, you may also need the Reveal Pet Quirks Mod.

An example command that removes an obsession with the doorbell is
traits.remove_trait trait_PetQuirk_Obsessed_DoorBell
An example command that adds an obsession with the doorbell is
traits.equip_trait trait_PetQuirk_Obsessed_DoorBell

Hope these examples are enough to understand the layout of the command!

List of Traits
Don't feel like writing it in yourself and just want to copy-paste?

Quick Remove Trait Commands
Quick Equip Trait Commands

I'm so happy that I found this, and I hope that you are too!

PS: It has been brought to my attention that your pets fears and obsessions may reset whenever doing certain actions like editing the household in CAS, or moving to a new location. The only fix for this is to just remove the fears and obsessions again. :/ Maybe someone could create a mod that fixes this bug. I'd love to create the mod myself, but I don't know how.

Awesome, this is really helpful and well written! Thank you very much. This has actually prompted me to give the controllable pets mod a look.

Thanks for the feedback! : )

In the controllable pet mod, my puppies play as children. Also, my puppy is obsessed with minor pets, and I can't change it. Maybe you can help me with that?