1. Monkey business: silly, mischievous or dishonest behaviour.
Example: All right, enough monkey business! We've played and joked around long enough. It's time to settle down and get serious.
2. To bury the hatchet: to agree to stop arguing; to stop being unfriendly and become friends again.
Example: Let's bury the hatchet, ok? I'm tired of fighting with you like this.
3. To add insult to injury: to make a bad situation even worse by saying or doing more harm.
Example: My friend arrived an hour late to lunch. Then, to add insult to injury, he started complaning about my choice of restaurant.
4. Speak you mind!: tell me your opinion, frankly and clearly.
Example: She's very opinionated - and she's not afraid to speak her mind, too. She tells exactly what she thinks!
5. You stole my thunder!: You got the attention or praise that I expected by doing what I had intended to do.
Example: I kept about my friend's wedding plans, she wanted to anounce the good news herself, and I didn't want to steal her thunder.
6. A wolf in sheep's clothing: a person who acts friendly and harmless - but who is really a dangerous enemy.
Example: I wouldn't trust him for a minute - he's just a wolf in sheep's clothing. He acts like he's your friend, but he's really trying to sabotage you.
7. To laugh your head off: to laugh loudly, to laugh for a long time.
Example: The show was just hilarious - we were laughing our heads off all the way through!
8. In the doghouse: in a position of disfavour, shame or trouble.
Example: You forgot your wife's birthday? Now you're really in the doghouse. Just get her some flowers and tell her you're sorry.