Characters: (*=main)

*Thomas Tank:
17 yeard old, Well-Known student, Percy and Toby's best friend, Emily's future boyfriend (Season 3-4), Annie and Clarabel's older brother

Edward Blue:
Student Council President, best friends with James

Henry Green:
Morning and event announcer, aquaintence of Gordon

Gordon Big:
Captain of the Basketball Team

James Red:
Drama club president

*Percy Small:
Thomas and Toby's best friend, Molly's new boyfriend (Season 2)

*Toby Tram:
Thomas and Percy's rich best friend, Mavis's boyfriend, rich family,

Duck:
The Great Western, Oliver's lab partner

Donald and Douglas:
Scotish twins, Tennis doubles partners

Oliver:
Band's drum line leader, Duck's lab partner

Diesel:
School Bully

Bill and Ben:
Schools Pranksters, Twins

Boco:
Coolest kid in school, beach lifeguard, Makes Bill and Ben behave

Daisy:
Teacher's Pet, head of the cheer squad, crush on Thomas

Stepney:
Foreign exchange student

*Emily Beautiful:
new girl (1st episode),Thomas's next door neighbor (2nd episode-Season 4), Thomas's future girlfriend (Season 3-4)

Spencer:
School show-off

*(Season 2-4) Molly:
Percy's new girlfriend

Rosie:
idolizes Thomas, but loves Oliver

Whiff:
Garbage kid but respected by Thomas and co., crush on Daisy

Annie and Clarabel:
Thomas's four-year-old twin sisters, never do anything without the other

Henrietta:
Toby's five year old sister, Annie and Clarabel's friend

I have a list of people I know who would suit these roles.