Timmy and Tommy Tibble

 Tommy Tibble  and  Timmy Tibble  are energetic twin brothers in D.W.'s preschool class. Together they are known as the Tibble twins or the Tibbles. They are the main antagonists of D.W.'s own episodes.

Physical appearances
Timmy and Tommy 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. Even when wearing different clothing, they always wear something blue and red. It is implied that even Miss Morgan cannot tell them apart when they switch scarves.

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.

In one episode, they both wear blue jeans with a yellow stripe and dark-grey sneakers. Timmy wears a blue shirt, while Tommy wears a red one, each with yellow design.

Personalities
Timmy and Tommy are mischievous, clever, reckless and often really mean and annoying (sometimes one more than the other), 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". "Two Minutes" and "Whistling in the Wind" reveal that Tommy is two minutes older, causing him to act superior to Timmy in both episodes. In "Double Tibble Trouble", Tommy is less energetic and feels sad when Timmy is sick, 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.

Their personalities can be described as manipulative (for instance when they trick people so they can get what they want as is seen in several episodes, including "To Tibble the Truth"), dishonest, and sadistic. They could even be described as fair weather friends (which refers to someone who only helps when it's advantageous to themselves) as is the case in "Never, Never, Never" where they trick D.W. into thinking they care about her in order to get her toys and destroy them in front of her face. Normally their personalities are identical except for a few episodes, e.g. "My Fair Tommy" where Tommy is slightly nicer and Timmy is more manipulative.

Appearances

 * Specials
 * "Arthur's Perfect Christmas"
 * "Arthur - It's Only Rock 'n' Roll"
 * "D.W. and the Beastly Birthday"
 * "Arthur and the Haunted Tree House"
 * Season 1
 * "Arthur and the Real Mr. Ratburn" 10201
 * "D.W. All Wet" 10301
 * "D.W. the Copycat" 10502
 * "Arthur Babysits" 10901
 * "D.W.'s Baby" 11102
 * "Arthur's Lost Dog" 11202
 * "So Long, Spanky" 11301
 * "D.W. Flips" 11602
 * "D.W. Rides Again" 11901
 * "D.W. Gets Lost" 12402
 * "D.W.'s Blankie" 12701
 * "My Club Rules" 12901
 * Season 2
 * "Go to Your Room, D.W." 20402
 * "Play it Again, D.W." 20602
 * "D.W.'s Deer Friend" 21101
 * "Arthur vs. the Piano" 20801
 * "Water and the Brain" 21301
 * "D.W.'s Name Game" 21901
 * "Sue Ellen's Little Sister" 22002
 * Season 3
 * "D.W. All Fired Up" 30201
 * "I'd Rather Read It Myself" 30202
 * "The Chips are Down" 30501
 * "Revenge of the Chip" 30502
 * "Attack of the Turbo Tibbles" 31001
 * "Double Tibble Trouble" 31101
 * "Arthur's Almost Live Not Real Music Festival" 31102
 * "D.W.'s Perfect Wish" 31402
 * Season 4
 * "D.W.'s Library Card" 40101
 * "Buster's Breathless" 40301
 * "Prove It" 40402
 * "D.W. Tale Spins" 40601
 * "1001 Dads" 40801
 * "Prunella's Prediction" 40802
 * "What is that Thing?" 40901
 * "My Music Rules" 41001
 * Season 5
 * "Arthur and the Big Riddle" 50101
 * "Nerves of Steal" 50202
 * "You Are Arthur" 50502
 * "Sleep No More" 50701
 * "The Last of Mary Moo Cow" 50801
 * "Just Desserts" 50901
 * "Arthur's Family Feud" 51001
 * Season 6
 * "Arthur Plays the Blues" 60201
 * "Buster's Sweet Success" 60202
 * "The Boy Who Cried Comet" 60501
 * "D.W.'s Backpack Mishap" 60602
 * "More!" 60702
 * Season 7
 * "To Tibble the Truth" 70401
 * "Elwood City Turns 100!" 70500
 * Season 8
 * "D.W., Dancing Queen" 80402
 * "Sue Ellen Chickens Out" 80502
 * "Desperately Seeking Stanley" 80702
 * "Tales from the Crib" 80802
 * "Kiss and Tell" 80902
 * "Bleep" 81002
 * Season 9
 * "The Law of the Jungle Gym" 90302
 * "My Fair Tommy" 90402
 * "Arthur Makes Waves" 90601
 * "Emily Swallows a Horse" 90802
 * "D.W. Beats All" 90901
 * "Breezy Listening Blues" 91002
 * Season 10
 * "Happy Anniversary" 100100
 * "The Secret About Secrets" 100302
 * "D.W. Aims High" 100501
 * "D.W., Bossy Boots" 100702
 * "Operation: D.W.!" 100802
 * Season 11
 * "Germophobia" 110102
 * "Mind Your Manners" 110202
 * "Buenas Noches, Vicita" 110301
 * "Baby Kate and the Imaginary Mystery" 110501
 * "Dancing Fools" 110602
 * "Hic or Treat" 110701
 * "D.W. On Ice" 110901
 * Season 12
 * "Never, Never, Never" 120102
 * "Room to Ride" 120201
 * "Ungifted" 120402
 * Season 13
 * "The Good, the Bad, and the Binky" 130402
 * "D.W. Swims with the Fishes" 130602
 * "A Portrait of the Artist as a Young Tibble" 130701
 * Season 14
 * "D.W. Unties the Knot" 140202
 * "D.W., Queen of the Comeback" 140901
 * "In My Africa" 140902
 * Season 15
 * "Fifteen" 150100
 * "Whistling in the Wind" 150202
 * "The Last King of Lambland" 150302
 * "Muffy's Classy Classics Club" 150801
 * Season 16
 * "All About D.W." 160301
 * "Blockheads" 160302
 * "Night of the Tibble" 160501
 * "Read and Flumberghast" 160502
 * "On the Buster Scale" 160802
 * Season 17
 * "Waiting for Snow" 170602
 * "Brain Freeze" 171002
 * Season 18
 * "Best Wishes" 180401
 * "Two Minutes" 180701
 * "Messy Dress Mess" 180702
 * "Tibbles to the Rescue" 180802
 * "The Pageant Pickle" 180901
 * Season 19
 * "The Last Day" 1910
 * Season 20
 * "Fern's Flights of Fancy" 200201
 * "Bunny Trouble" 200302
 * "That's MY Grandma!" 200402
 * Season 21
 * "The Lost Dinosaur" 210601
 * "The Princess Problem" 210602

Family
Timmy and Tommy live with their grandmother in a large house that looks almost haunted.
 * Mrs. Tibble: Timmy and Tommy'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. The Tibbles do not tell her about their misbehavior, and when they do, they censor it to not sound like bullying. In "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:" Timmy and Tommy'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.

Friends

 * D.W. Read: Timmy and Tommy are her friends, but often try to compete with and pester her. They bully her in "D.W., Queen of the Comeback", and scam her out of all her toys (which they then destroy) in "Never, Never, Never".
 * Emily: She is D.W.'s best friend. They often try to compete with her as well.
 * James MacDonald: In "Night of the Tibble", James is invited to a sleepover with the Tibbles. They are genuinely excited about it, and tire themselves out while preparing for his visit.

Timmy Tibble

 * 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"

Tommy Tibble

 * 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"

Trivia

 * 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 to whistle during the course of these episodes.
 * Tommy and Timmy take folk music lessons. Tommy plays the panpipes.