merry as a cricket
old-fashioned Jubilant; especially carefree, lively, and full of fun. Tom is playing outside, merry as a cricket. Though he acts as merry as a cricket, he is dreadfully unhappy when he is all alone.
*merry as a cricket
and *merry as the day is longvery happy and carefree. (*Also: as ~.) Mary is as merry as a cricket whenever she has company come to call. The little children are as merry as the day is long.