1. as easy as ABC
- very simple and easy
- i.e.)don't worry about learning how to ride a bike. it's as easy as ABC once you get going
2. as easy as pie
- extreamely easy
- i.e.) no problem. i will show you to how to do this tomorrow. don't worry! it's as easy as pie
3. as genuine as a three-dollar bill
- fake, as three-dollar bills do not exist
- i.e.) Tom was showing us many of his antiques, telling us that they are rare and expensive. in my opinion, though, some of them are about as genuine as a three-dollar bill
4.as happy as a calm
- happy and content
- i.e.) don't worry about the kids. they're as happy as clams playing video games in the other room
5. as quiet as a mouse
- very quiet and reserved
- i.e.) she is as quite as a mouse. it seems like she hardly ever speaks
<Reference>
- The book "THE GREAT BOOK OF AMERICAN IDIOMS" BY Lingo Mastery