Shelldon

• Shelldon Clam (voiced by Tabitha St. Germain) is a young shellfish that lives in a hotel called the Charming Clam Inn with his family. He likes helping his friends and solving problems.
• Herman (voiced by Richard Ian Cox) is a blue hermit crab with an immense infatuation with "alien" artifacts and "paranormal" events. He has a crush on a classmate Hurly.
• Connie is a seasnail who comes from a wealthy family, but decided to work at the Charming Clam Inn, so she could do more than rely on her parents' money.

• Dr. Shell (voiced by Lee Tockar) is a brilliant yet scatter-brained riversnail inventor and a guest in the Charming Clam ever since it was set up and has become something of a permanent resident there. He has traveled widely across the seas in search of inspiration but not interested in making money, only the social benefits his inventions bring to others.
• Mama Clam (voiced by Ellen Kenndy) is a magnolia mollusk clam who lives and runs the Charming Clam Inn with her husband and three children. She is a cool-headed wife and mother who is not easily daunted by hardship or challenges. Raised in the cut-throat, fast-paced Shell City, Mama Clam is savvy, a careful planner who always seems to know the perfect solution to a problem. At home, Mama prefers to take a back seat and to let her husband run the household. However, being a shrewd housewife, she knows exactly how to manipulate Papa into doing her bidding. Mama is a total failure when it comes to cooking, yet she remains oblivious to the dire effects of her cooking, made worse by the fact that everyone in the family tries to hide it for fear of hurting her feelings. Her abject lack of culinary skills is a running joke in the series.
• Papa Clam (voiced by Colin Murdock) is a muddy-brown mollusk clam that lives and runs the Charming Clam Inn with his wife and three kids. He is guileless, none too bright, and crass at times. He is easily frazzled by setbacks and his solutions to problems tend to border on the impractical.
• Mr. Inkysquid (voiced by Scott McNeil) is a green squid that teaches the school.
• Mayor Yoka is a snail.
• Hurley is a prissy seasnail who obsesses over her nails and hair, which causes her to forget about her peers.

Min Min is a pink shellfish that sometimes appears in the show. She has a crush on a classmate named Herman.