Good question, Santa Klaus (cute name too).

I agree with Playfulsub that it depends on the character. And, of course how many characters you have and how and when they are introduced. I guess knowing how to do that is one of the talents that separate the good authors from the not so good authors.

The quicker you are able to establish a character’s personality the easier they will be to remember.

I think too that if you can plant a picture in the reader’s head it’s often easier to remember them--that is, a little bit of physical description.