Speak of the devil!

When a person has been talking about someone, and then that person suddenly appears, the person can say, "Speak of the devil!" If you walk up to a group of people and someone says this, you know they've been talking about you.

Example:
-What is Patrick going to do after he graduates?
-Well, first he wants to do some traveling with some friends, and then he'll move to Manhattan to.... Speak of the devil! How are you, Patrick?

Pretty please!

'Pretty please' is an expression that mostly kids use when they really want something and are trying to convince their parents. 'Pretty please with a cherry on top' is an extended, and even more pleading version.

Example:
-Mom, can I spend the night at Catherine's house tonight?
-Well...
-Pretty please!

Bat-shit crazy

'Bat-shit crazy' is used to describe someone who you think is just plain crazy and beyond any hope of getting better. In reality, it's not usually used to describe a person who is truly mentally ill, but rather a person who has such outlandish, uninformed and offensive beliefs that you're sure they must be crazy.

Example:
-That presidential candidate is bat-shit crazy!
-I know! If he wins, I'm moving to Canada!

Gold digger

A 'gold digger' is a person who wants to marry a wealthy person. Sometimes it's with the intent of living a better lifestyle, and sometimes it's planned in advance to later get divorced and try to get as much money out of the person as possible. This is why many extremely wealthy people sign a pre-nup (prenuptial agreement) before they get married, which states who gets what in the case of a divorce.

Example:
-I can't believe that 22 year old model married that 80 year old man. Eww.
-What a gold digger! His family must be furious!

Douchebag

A 'douchebag' is a serious insult to a guy, meaning he is a complete (fill in explicative here). A douche is a product sold to clean a woman's vagina. This term is extremely derogatory and should only be used in informal situations.

Example:
-My roommate threw up on my bed again.
-What a douchebag!

Living under a rock

To say someone is 'living under a rock' means that they have not kept up with current events, trends or beliefs because they have kept themselves isolated or simply don't care. It is pejorative.

Example:
-Can you believe he still thinks it's okay to beat your children?
-What rock has he been living under?

To get in the middle of it

'To get in the middle of it' means you get pulled in to an argument between two people that really has nothing to do with you.

Example:
-Mom, she called me stupid!
-Well, she said I was fat!
-Look, you two, that was't nice of either one of you, but I'm not going to get in the middle of it. You two need to figure it out and apologize.