I also do this, on a lesser level, with letters and days of the week.
Monday, Wednesday, Thursday, Saturday Sunday: Girls. Tuesday, Friday: Boys.
A, C, G, H, I, K, M, N, O, Q, T, V, W, X, Y, Z: Girls.
B, D, E, F, J, L, P, R, S, U: Boys.
For the most part, though, I haven’t assigned personalities to the letters. But I can tell you that J is the super popular guy in school, I is the annoying freshman girl who follows him around like a lovestruck puppy, and H is her ugly, fat friend.
I know I’m not the only one, since there’s a Wikipedia entry on it (and Wikipedia would never lie), but I’m curious if any of my readers experience this.