The Main Characters - Found in All the Books
- Alvin Fernald - Inventor, Secret Agent, TV Anchorman, Crytographer, Master of a Thousand Disguises. Alvin and his "Magnificent Brain" always find themselves the central figure in any mystery around Riverton.
- Wilfred "Shoie" Shoemaker - The Greatest Athlete in Roosevelt School, and Alvin's best friend.
- Daphne Fernald (The Pest) - Alvin's little sister, a tomboy, who worships everything that Alvin does. Frequently it is The Pest who comes to Alvin's aid when things go wrong.
- Sergeant John Fernald - Alvin's father, a sergeant in the Riverton Police Force. Sergeant Fernald is very proud of Alvin, and is frequently the only adult who takes him at his word.
- Mrs. Fernald - Alvin's mom. Always there with a plate of warm cookies. Worries because The Pest wears Alvin's old bluejeans and carries a football, rather than wearing dresses and carrying a doll.
- Al Moser - Ace reporter and photographer for the Riverton Daily Bugle. Seems to have a special ability to turn up for each of Alvin's adventures.
- Mrs. Huntley - A feeble old lady who lives in a huge run-down house in Riverton. A very gentle lady, she loves birds and believes that her husband was reincarnated as a bird.
- Mrs. Huntley's Nephew - The "bad guy" who holds Mrs. Huntley hostage to steal her money.
- Mr. Link - A warm man with a huge head, who is a parapalegic. Mr. Link is a former intelligence officer who teachs Alvin, Shoie and the Pest about codes and ciphers.
- Mrs. Murphy - Mr. Link's housekeeper.
- Alicia Fenwick - Runs an orphanage in the South. Presents Alvin with the story of her grandfather, Elijah Fenwick and his slave, Adam Moses, who left a buried treasure behind at the end of the Civil War.
- Miss Jackson - The Riverton Librarian, who shudders whenever Alvin enters the library.
- Mr. Smith (alias Hitchcock) - The "bad guy" who is willing to do anything to find the treasure.
- Melvin Trimble - President of the Kitchenmate Appliance Company.
- Mrs. Trimble - Melvin's wife. Joins her husband, Mr. Beasley and the kids in their tour of Europe.
- Bixby B. Beasley - "Busy as a Bee"! Director of Public Relations for the Kitchenmate Appliance Company.
- Miss Pinkney - Alvin's teacher.
- Mr. "X" - The "bad guy" who followed the kids as they traveled through Europe. Mr. X is an industrial spy, targeting the Kitchenmate Appliance Company and their European partners.
- Herr Hoogendoorn - a Dutch industrialist and inventor. Has invented a special metal that he wants to sell to Kitchenmate.
- Piet Hoogendoorn - Herr Hoogendoorn's son. A great bike rider. Becomes a good friend to Alvin, Shoie and the Pest.
- Miss Pinkney - Alvin and Shoie's teacher.
- Speedy Glomitz - Alvin's campaign manager. It was Speedy's wheeling and dealing behind the scenes that helped Alvin to get elected.
- Mayor Melbourne Massey - The mayor of Riverton.
- Miss Carner - Mayor Massey's secretary.
- Theresa Undermine - Alvin's opponent in the mayor's race.
- Worm Wormley - Alvin's friend and aide. Worm is a stutterer who served as Alvin's Chief of Police.
- Spider Funsterman - Alvin's Commissioner of Public Works.
- Alicia Malienchowicsky - Alvin's City Treasurer.
- Hortense Pillsberry - Alvin's City Clerk.
- Peanuts Dunkle - Alvin's Fire Chief.
- Miss Miles - Alvin's teacher
- Windy Biggs - Alvin's long-winded classmate, and the son of one of Riverton's greatest polluters.
- Randolph E. Biggs - Owner of a chemical plant in Riverton. Windy Bigg's father.
- Mayor Homer Bienfang - Mayor of Riverton
Alvin's Swap Shop
- Elmira - A tiny ant that started the adventure.
- Turkey Otto - Alvin, Shoie and the Pest's first customer. Swapped a collection of spiders for Elmira.
- Tubby Tubbs - Provided a store for Alvin's Swap Shop, in return for a bunch of square dance music.
- Pim Bethel - A young man from Eleuthera, Bahamas. Central character in the search for a treasure that he doesn't even know that he has.
- Scarface - A "bad guy" who wants to find Pim to steal his treasure.
- Mr. Pogue - Boat owner, supplied books to Pim. Killed by Scarface.
- Brian Talley - A truck driver who helped Pim get away from Scarface.
- Sergeant Ellsworth - Sergeant on the Riverton Police Department.
Alvin Fernald, TV Anchorman
- Don Brooks - Local television anchorman.
- John Kubec - A cameraman at the local television station. Helps Alvin and the kids learn how to put together a television show. Central figure in the mystery.
- Pete Hardin - Alvin and Shoie's soft-spoken classmate. Producer and writer for the Junior News Team.
- Lou Bessimer - General manager of the local television station.
- Miles Sullivan - Chief anchorman for the IBS Television Network.
- Scott Lewis - IBS anchorman in Santa Maria.
The Wacky World of Alvin Fernald
- Abraham Joker - Former Mayor of Riverton. Master of practical jokes.
- Mayor Brock - Mayor of Riverton.
- Humphrey Dexter Grubbs III - Alvin's greatest invention!!!
- Worm Wormley - Alvin and Shoie's friend. Provides a voice to Humphrey.
Alvin Fernald, Master of a Thousand Disguises
- Christina Moller - Central figure in the mystery.
- Ada Scheuneman - Christina's great-great-grandmother.
- Tim Martin - Ada's love. Woodworker who made a special clock. Died after burying the treasure.
- Beardface - The "bad guy" who is trying to steal Tim Martin's grubstake from Christina.
- Broken Nose - Beardface's accomplace.
- Kelvy Brown - Lead carpenter for Alvin's greatest disguise.
