A joyous me and a concerned puppy headed home, and I told him right off, "I have a cat. I heard you're okay with cats, so this should work."
Petey has this thing he does (I don't know what to call it) where he raises his shoulders, his tail is erect and the whole body posture communicates "I'm in charge." (This is why I'm inclined to call him "Sgt. Pete.")
He approached Mosie like this, and I warned, "Good luck with THAT!" Mosie and I have gone 'round and around about who's in charge of this household, and I've always come out the loser. So at first meeting, I kept Petey on the leash in case I needed to grab him up if Mosie felt inclined to assert her authority with a painful swipe. First encounter went well.
Then I discovered he loved her cat food. So up she went until I could come up with another plan.
Mosie didn't speak to me for the month after Petey arrived. He tried to play with her, but she's too sophisticated for such. The more he tried to play with her, the more it irritated Mosie. It took a while for Mosie and me to adjust to this little yellow "twister" who would blow through the house with sharp barking, throwing himself at the door (BAM!) to go out, or volumizing his favorite squeaky toy I named, well, "Squeaky."
As I stated earlier, my expectations were to own another calm, obedient, orderly dog.