I think I figured it out to make NPC stray pets WITHOUT Mods!
As I was a kinda disappointed to see that you cannot really create stray pets at first when I was trying to create wolves and foxes-like dogs to my stoneage gameplay.
But until today,I finally figured it out how to do this with only cheats(like testingcheatsenabled true and ageuptonpc)!
And it works with my patch version 1.67!
Okay, so hereÂ´s what you want to do:
1. Start the game and choose which gamefile you want to play with.(But I highly recommend to choose a new file if you donÂ´t want to switch households)
2. Either create a new household including these sims: a young adult sim, a toddler sim and as many pets you want(up to 6 pets is allowed!)and place them on a lot. Start play with this household.
3. Now push shift+Ctrl+c to get the cheatbar.
4. Now enter: testingcheatsenabled true.
5. And then enter: ageUpToNPC.
4. Shift-Click on your toddler sim and choose: trigger age transition.
5. The toddler sim will now age up to child and when the "celebrate" interaction is done for the sim,do the above instruction repeatedly until your sim reaches young adulthood!
6. Now,you're gonna kill or delete the older young adult sim you created first in CAS. Drag the Hunger bar all the way to the left.But you can also try to Shift-Click on the sim and choose delete it under the object menu.You have to wait until the grimreaper has left.
7. Now,you can go to edit town and save your household to the bin.
8. Return to main menu.
9. Start a new game where you want these sims to be in.
10. Place them on a residental lot and then evict again.
11. Once again, return to main menu and choose your town again.
And now you should have(if done everything correctly)these pets as stray animals in your new town! Even the NPC petowner should be there too.)
If you want to be sure this is working,choose one already existing household(but never choose your newly made NPC-household copy,as you won't actually be able to play with this household)and shift-click on the mailbox and choose: let me know everyone. You can now see if these sims exists in your town this way! They should also be running around town. I haven't tested this entirely yet,and maybe if you're interested to know more,I will edit this in the future.
This has been tested by me,and if you are interested to try. You will do it at your own risk! But I donÂ´t think you're having some corruption with this method. It was just a warning as I just have been figured this out today!
And, you can correct me if you might won't understand me clearly. My english is bad certain days.
I hope this helped some bit,I just wanted to help you to make your own stray pets in your sims games!