lark it up
To have a very fun, enthusiastic, and lighthearted time. I'll always think back fondly of the summer after high school, larking it up each week with my friends all around town. The boss chastised us for larking it up instead of getting to work on the project.
lark it up
Also, lark about. Have a noisy, exuberant good time. For example, We were larking it up when the supervisor walked in, or He's always larking about at night. These expressions employ lark in the sense of "to frolic," a usage dating from the early 1800s. Also see cut up.