I'm glad you're doing this while Luna is still young, Kirsten. My Mimi was not a happy camper when we tried to introduce a new kitten about 7 years ago. Dwayne was a rescue (we got him at three weeks old), but we eventually had to rehome him because Mimi lost her mind about him. But, as Mimi has gotten older (she's 13 now), she has settled down, and when Butter showed up here year before last, she never liked him, but tolerated him, and still does. She is not good friends with him. She hisses at him every time he is near her. But, she does co-exist at this point. I hope your experience will be much better with Luna. I'm sure it will be!