Barnabus is a Bucket Crab, living on the sea shore, and therefore can be found in and around the local rock pools.
Crabs of many shapes and colours are in these pools. Most importantly, they can be carefully caught with a net. . . or by hand, if a person is brave.
The usual established practice of rockpool explorers, is to catch crabs and pop them in a bucket for a while. Sea water is added to keep them cool and happy.
According to “The Everlasting Poo” video, all the crabs are Bucket Crabs. In addition, they all seem to want to be called Barnabus. The extra sketch, starting at 4:29 after the rolling credits, reveals this.
Several of the Bucket Crabs have middle names. For instance, Barnabus the ‘handsome’ Bucket Crab, stars in the main video. However, Barnabus the rascal Bucket Crab stars at the very end of the extra sketch. . . having caused a bit of friendly trouble.