1.A monkey on one's back
Eric is a workaholic. He needs to get the monkey off his work.
2.Monkey business
There is been some monkey business connected with his tax returns.
3.Monkey around
The kids are just monkeying around,playing and throwing things at each other.
4.Monkey see,monkey do
Big Brother:Why do you keep copying everything I do?
Little Brother:Monkey see,monkey do!