Dee and Dum have very similar appearances, and if not for their different eye colors- Dee has blue eyes and Dum has red eyes- would be impossible to tell apart in child form if they were to dress alike and speak alike. As they are not identical twins, however, their eye color is one of the ways to tell them apart. In child form, they have short black hair and uniforms that are near mirror images of each other, except that Dee's is in blue and Dum's is red and the chain on the front of the uniforms is identical. In adult form, Dee wears his hair longer and tied back with a blue ribbon while Dum's hair is shorter, black and red barrettes holding back his bangs on one side.

The twins are childishly cruel, yet retain a sort of innocence in their cruelty. This innocence does not extend to their actions towards Alice, for when they grow especially attached to her, they do not behave as children. They like to skip work and kill for the fun of it, saying their are playing with whomever had the misfortune of being their victim. Both twins prefer axes to guns, "because axes are more fun." They look up to people who are mature or who benefit them, but everyone else (except Alice) will be subject to their insults and/or teasing. Because they are young, they are spontaneous and live more in the moment than most other people.

While not much is known about their pasts, at one point they were shunned by people 8for being too creepy. This leads them to expect Alice to abandon them at various times throughout their routes.

At some point, they formed a contract with Blood to guard the gates to his mansion. While the specifics of the contract are not clear, they seem relatively pleased with it.

When the twins find her they are happy and call her Big Sis/Onee-san. In their single volume manga Bloody Twins, they enter the bath with her and scare her. At first Alice has no clue who the twins were and was scared to be with them but then they scare her more when she finds out that the older twins are really the same twins she has always known.

In the game, the twins often play hooky from the entertainment (the Assembly) and play in town. It is here that they reveal their ability to change their ages and they switch from young children to young men as they please. Alice has to come to terms with their viciousness as adults, as well as their innocence as children.

In the Country of Diamond, the twins are only adults. Their personalities are the same as ever, but they are far more uncaring towards Alice and do not smother her with affection.

Tweedle Dee and Dum see each other as a single entity, meaning that when they fall in love, they fall in love with the same person. However, this doesn't stop them from from having several differing preferences (like favorite color or ice cream flavor) and saying that they will fight to the death if Alice wants only one of them.

It is mentioned by Crysta that the Tweedle twins are the only pair of adult twins in the Country of Diamonds. In other words, either the Tweedles are the only pair of twins in that time period or that there is another set of twins, only that pair must be just children. In this world, they stay adults

The Tweedles have no cooking ability whatsoever.

They like to talk

Their hair is black.

Their eyes don't glow.

They're both 6'2" tall

They're about the same age of 18-24years old. They're young adults...

Dee has blue eyes, long black hair, wears a blue tie and wears his hair in a ponytail.

Dum has red eyes, wears his hair short with a few clips holding his black bangs in place and wears a red tie.