Drat! Foiled again!

A few months ago I won a full manuscript critique from Michelle Argyle. She sent it back with fantastic notes and ideas. Still, I was overwhelmed with the thought of revisions. My critique group suggested I set the story aside for a little while and look at it anew later.
I was going to follow their advice, I really was! Until I listened to a Writing Excuses podcast on foil characters.
What the heck?
The image of Joaquin Phoenix in a tinfoil hat came to mind. But that isn't what the podcast was teaching me.

Foil - a character that is used to enhance another character through contrast, highlighting strengths and weaknesses. Create characters in pairs like the straight man and the comedian or Cinderella’s grace and beauty as opposed to her nasty, self-centered stepsisters.

Here are a few other examples of foil characters:
Batman & Robin
Sherlock Holmes & Watson
Danny Glover and Mel Gibson (Lethal Weapon)
Wise mentor & newcomer
Siblings

The last example is the one that perked up Le Muse from a sleepy state of boredom. Siblings! I need to add a a sibling.
My story centers around Mandy, a girl who found out her mother is really an alien impostor and her father has been with holding this secret for years. She didn't want to believe there were aliens taking over her town or abducting boys until her father is taken.
Not really intense. But! Add a teasing brother who drives his sister nuts and not only believes in aliens but claims to have seen them. Mandy makes fun of him.  Not until the brother is abducted does she have to face the facts and save the day.
I'm happy to say I'm ready to do revisions now. Well, the job is still overwhelming but now I can move on to the next step and make this story better!

What foil characters come to your mind?  Do you have them in your story?

PS Don't you LOVE Joaquin in The Village? Best. Romantic. Scene. Ever.