For those of you who have successfully added a second adult cat to your household with an existing adult cat: what personality/sex combos worked for you? I know it's a bit of a coin toss when it comes down to it, but I want the best chance of success as far as I can control. My existing cat is 4 to 6 years old, playful, affectionate, very attention-seeking, and I believe she will be quite guarded/territorial at first. I'm hoping to find her a companion who can keep her company during the day and play with her the way she wants to be played with. Should the new cat be older or younger? Male or female? Smaller than her or larger? Calm or more energetic? Mellow or feisty? I have some idea, but I know some of these may not matter as much as I think they will, and that cat chemistry can be luck-of-the-draw even if you do everything right.