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.
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. 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.
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.