They appear in the episode "Choir Boys," where Squidward auditions to be a choir boy, but only to be failed, and for SpongeBob to be chosen. They also appear in the episode "A Day Without Tears" driving in their boat car. They gather regularly at their Choir Studio that looks much like a small church. After all practices, they have a season of performances at their usual open-air concert hall in Bikini Bottom. They wear mustaches and red bowties and wear no shirts.
In the episode "Choir Boys" they are first seen on a picture wearing different clothes that are the same as the clothes that Squidward wore. Also, they didn't wear shirts in that episode, unlike Squidward.