I got a premade custom world (Petlandia) and I'm editing lots to put people in but some of them have these silver orbs that I can't move, and it tells me that I can't edit those rooms or floors. One lot even did that to me with the outside of a house.

I'd really like to play this world, especially since I made a park for it, but I'd like to make the houses more custom and that means letting me add stuff to vacant floors. How can I get rid of those stupid silver balls?

These silver orbs are markers for e.g. skipped floors. If you want to edit these lots you will have to enter a cheat. It's the same mechanism as if you wanted to edit an apartment lot.

While in normal gameplay, press CTRL+Shift+C to open the command console. Enter testingcheatsenabled true and hit return, then open the command console again but this time enter RestrictBuildBuyInBuildings off. Now the game will let you edit those lots. If you're done, open the command console again and type testingcheatsenabled false.

Ah, thank you!