Actors/ Actresses

I am hoping to film with two male characters, as that's how I wrote the story. Two male characters both named Brian.
However, I'm toying with the idea of having Brian (2) as a female. It will add a little comedy/ confusion to the film.
I can change the script, or add in little parts of speech such as: Brian (2): "Didn't you think it was a bit weird I'm a girl, and my name is Brian..."

Also, it gives confusion in the form of questions like: Are they boyfriend and girlfriend, are they brother and sister etc. This is good for the style of my film, as when they realise Brian (2) is completely made up it will both answer the question's of their relationship, and answer the question of Brian (1)'s sanity.
Also, I know a male and female that may possibly be available whereas I don't know two males that want to and will be able to.
If I had a girl and a boy, it would solve some difficulties however I would have to edit the story, and script a little to accommodate the change in character.