I have 5 cats:
Berkley is always wherever I am so she is hard not to find
Sterling is usually laying in the middle of the floor on his back with his belly ready to be rubbed.
Coco is usually on the top level of the cat tree, she is the hardest to find, she likes to hide under beds and sofas and she is black so she isn't easy to see find if she is hiding.
Sasha is a little busy body. He doesn't hide, just plays in every place imaginable. When he sleeps he lays right in the middle of the floor so he is easy to find
Peaches is in her own room so she can't go too far.
If I need to find all of them at once, I go to the kitchen and rattle the food dishes and they all come running instantly.
Oh, about thier names, I noticed not too long ago that all five of them have different sounding names. They all "end" with different sounds as opposed to all ending in EY for example
Good idea about making up thier birthdays! I will do that tonight. I have an idea of about what time of year they were all born!