More fun than a barrel of monkeys

This expression using a number of different collective nouns for monkeys e.g. cage, box, wagonload, barrel-load, etc has been around since the mid-19th century, Specifically, a ‘barrel’ of monkeys made it first appearance in the 1890s. Monkeys are renowned for their mischief and playfulness and any collective noun for them naturally reflects this. It may also have been influenced by barrel of fun.