1. They'll always back up whatever ridiculous lie you tell your parents...
2. She's the ultimate fashion accessory.
3. She totally drives you nuts sometimes, but you'd jump to her defense anytime.
4. No matter how terrible your day is, she knows exactly how to make it better.
5. They'll hate someone simply based on the fact that you hate them.
6. You can use her ID whenever you lose yours.
7. She never judges you.
8. You ask her advice for any and all life changes.
9. Sometimes you don't even need words to communicate.
10. No one can get you fired up faster...
11. You have inside jokes and nicknames that go back decades.
12. They'll reassure you that whatever freckle you're obsessing over isn't cancer.
13. They're always up for whatever mischief you throw their way.
14. And the best thing about having a sister?
Tina Fey and Amy Poehler are the ultimate partners in crime in Sisters, in theatres December 18.
