|Timmy and Tommy Tibble|
Timmy (blue scarf) and Tommy (red scarf)
|Residence||Tibbles' house, Elwood City|
|Family||Trixie Tibble (mother),|
Mrs. Tibble (grandmother)
|Book debut||Arthur Babysits|
|Cartoon debut||"D.W. All Wet"|
|Voiced by||See text below |
Tommy and Timmy are bears in the show and humans in the book. They always dress identically. They normally wear yellow t-shirts, purple shorts, yellow socks, and black and white sneakers. As they are identical twins, Timmy always wears a blue scarf while Tommy wears a red one to differentiate. Originally in the books, they looked more like humans and less like bears, but that changed in the cartoon series. Notably, however, in even later book releases, they continued to appear as humans, despite the significant art shift in the books towards an appearance more in line with that of the television series.
Tommy and Timmy are mischievous, clever, reckless and often really mean and annoying (Timmy more than Tommy, but sometimes Tommy more than Timmy), though deep down they are good kids. Timmy is more independent and meaner than his brother, as seen in "Double Tibble Trouble" and "Attack of the Turbo Tibbles." In "Double Tibble Trouble" it is revealed that when Tommy is not with Timmy he becomes sad and behaves well, but at the end of the episode when Tommy gets sick, Timmy doesn't seem sad and behaves like always. In "Attack of the Turbo Tibbles," Timmy is the one who hurts D.W.. They each have their own ways of annoying others, usually by yelling louder than one another. Tommy also seems to have more of a sensitive side than Timmy.
Tommy and Timmy live with their grandmother in a large house that looks almost haunted.
- Mrs. Tibble: Tommy and Timmy's grandmother. She loves them very much, but doesn't always show awareness of their bad behavior, though she does occasionally show signs of distress at their actions. In the episode "Mind Your Manners", they force themselves to learn manners in order to take her out to dinner. They usually spend all of their time at her house when they're not in preschool.
- Trixie Tibble: Tommy and Timmy's mother. She is first mentioned in "D.W.'s Backpack Mishap", where we find out that she used to take them on trips around the world.
- Tommy & Timmy's Father: Although mentioned several times, not much is known about their father. 
- D.W. Read: The Tibbles are her friends but often try to compete with and pester her. They also sometimes trick her into doing foolish things.
- Emily: She is D.W's best friend. They often try to compete with her as well.
- Bud Compson: They officially trick him.
- Ricky Mabe: Season 1-5, Arthur's Perfect Christmas
- Samuel Holden: Season 6-9, Arthur - It's Only Rock 'n' Roll
- Tyler Brody-Stein: Season 10-11
- Chris Lortie: Season 12-13
- Dakota Goyo: Season 14-15
- Jacob Ewaniuk: Season 16-19
- Samuel Faraci: Season 20-present
- Max Henry Wolf: Arthur's Missing Pal
- Jonathan Koensgen: Season 1-6, Arthur's Perfect Christmas
- Aaron Grunfeld: Season 7-8, Arthur - It's Only Rock 'n' Roll
- Tyler Brody-Stein: Season 9
- Ryan Tilson: Season 10-11
- Jake Roseman: Season 12-13
- Jake Sim: Season 14-19
- Devan Cohen: Season 20-present
- Madison Danielle: Arthur's Missing Pal
- In the book series they're humans while in the television series they're bears.
- In "Bleep", Timmy can whistle, but in "Whistling in the Wind" he can't, however, it is possible that the events of the latter occurred before the former, or that Timmy might have learned whistling during the course of these episodes.
- In the newer episodes, Timmy is a little taller then Tommy. But they are the same size in the earlier ones.