i wouldn't have to explain anything to my parents, they don't know what movies i watch anyways, i just say i'm going to the movies and i'm out.
as for the characters, i don't think it's half as important to get the character resemblances as it is to get the character acting right. i think it's pretty obvious there will be resemblances, but we don't need them in the exact same wardrobe (as long as they don't resemble the people in the matrix, they should be fine)
some character's physical features that are plot-driven, now there is an argument, of course we will need misato to have her scar on her body, and we need Rei to be
different in some way, hopefully she'll be albino but we don't need bright blue hair (which would be distracting as someone said earlier and it is true), we just need a very light tint of blue in her hair to let us know from far away that it's her
i don't think for the character's roles that we should look for big names, some of the best character resemblances i've seen have been people that have been in theatre for a long time and suddenly make an appearance in film, so i'd say leave the casting to the caster. (assuming he's compatent) (sp?)