Question: what are the 20 idiomatic expressions?
Answer: Straight from the horse's mouth. Meaning: getting information directly from the most reliable source. ... 
Let the cat out of the bag. Meaning: to mistakenly reveal a secret. ... 
Butter someone up. ... 
Pulling someone's leg. ... 
Wolf in sheep's clothing. ... 
Hands down. ... 
Riding shotgun. ... 
Barking up the wrong tree.