Hop on the bandwagon
Egg on
As mad as a March hare
Run around like a headless chicken
Black sheep
Chickens come home to roost
Fly the nest
Teach someone’s grandmother to suck eggs
young person leaving their parents’ home to set up home elsewhere
become involved with or support an activity/cause that’s recently become popular
act in a panic-stricken, directionless manner
someone who’s viewed by the family or group as an outcast because of their behaviour
offer unnecessary advice to someone who’s older and more experience
crazy, eccentric
encourage someone to do something foolish or risky
one’s past mistakes will resurface and cause present troubles