A small, female outdoor cat that comes to the porch during the day to eat, whom I have named Franja, will sneak into the house whenever she gets a chance, but Ella hates her. Once, when I had the door open, talking to her, Ella got in front of me and vocalized something that didn't sound threatening to me, but which Franja interpreted as a demand to leave. Since then, when Ella is around, and I am feeding or socializing with a cat on the porch, she will check to see which cat it is. She's okay with it if it's Sobaka or Smoke, but does not approve of me feeding Franja.
A week ago, I was late feeding her, and Franja came looking for me upstairs by climbing the fire escape stairs. Ella was sleeping in a window bed by the fire escape window, facing away from it. I was in a chair working on my MacBook. Franja tapped on the window, probably to get my attention. Ella spun around and found herself face-to-face with Franja, with only the window separating them. She went nuts, and within seconds, both cats were slapping at the window, while Ella was screaming like she was in a battle for her life.
I went downstairs and outside to coax Franja off the fire escape, and, after feeding her, I went back upstairs to find Ella still all worked up over it, huffing and puffing.
Today, Franja had already eaten, and I was downstairs unpacking some boxes that had arrived when I heard Ella screaming upstairs. After eating, Franja decided to climb the fire escape stairs and annoy Ella again. To be fair, I don't know what her intentions were. Perhaps she was looking for me, or maybe she wanted to make peace with Ella. Either way, there was no peace to be made with Ella, who is not a Franja fan.
I don't know if she necessarily would be excited about either of them coming inside to live because cats can be weird about that sort of thing, but Ella has seen Sobaka in the house several times now. She usually ignores him, but when I called her over to meet Sobaka, who is a very large cat, while Ella is quite small, it went well. Ella came over when called (which means she wanted to because she does not feel obligated to come when I call her, otherwise). Sobaka positioned himself as low to the floor as possible without lying down, which seemed to be a sign of respect. Ella did the same, and they looked at one another for a while, with neither of them looking at all hostile. Then they stretched out far enough to touch noses. Then Ella walked away to lie down in a cat bed, as if she had satisfied her curiosity.
Usually, Sobaka comes in just as far as the landing or barely inside of my adjacent office, where he can eat without fear of being approached by another cat, or raccoon, or whatever it is that he's afraid of outside. When he comes in far enough to allow it, I close the door, and that doesn't seem to bother him. He places both paws on the door when he wants out. A few days ago, he spent about 20 minutes in the house, then didn't show up for a few days.
Ella has been introduced to Smoke through the door, although he has come inside only once. A couple of nights ago, while Ella was in the library, I invited Smoke in, and he immediately ran into the house and into my office, then, just as quickly, he ran back out again. Otherwise, Ella has been by the door while Smoke was in the porch, and they seem okay with one another, too. Several years ago, when Ella was allowed to go outdoors during the day, she didn't respond to my call when it was getting near dusk. I went looking for her and found her sitting only a few inches away from Smoke along the bank across the railroad bed. They seemed to be ignoring one another, but were clearly comfortable with proximity, given that there was no reason for two cats to sit next to one another outdoors.
As you might know from another thread, I have an opening for an outdoor cat to become an indoor cat, and my boss (Ella) seems to be okay with either Smoke or Sobaka, as would I. Smoke has been an outdoor cat for at least seven years now, while I think Sobaka has only been homeless since late winter or early spring, because that's when he first showed up here, very hungry and willing to be petted.
I have been feeding Smoke for about seven years, and he frequently lets me pet him or even pick him up sometimes, while, at other times, he acts like he's afraid I'm going to kill him. He hangs out with me in the backyard a lot. I'd love to take him in, but he has crossed the threshold only once and immediately retreated, while Sobaka seems more willing.
Ella would be okay with either of them, I think, but I don't know that they'd be okay with one another. Although Sobaka is larger and younger, he's afraid of Smoke, although Smoke doesn't seem to be hostile towards Sobaka.