The Dormouse is a character in "A Mad Tea-Party", Chapter VII  from the 1865 novel Alice's Adventures in Wonderland by Lewis Carroll.

The Dormouse sat between the March Hare and the Mad Hatter. They were using him as a cushion while he slept when Alice arrives at the start of the chapter.

The Dormouse is always falling asleep during the scene, waking up every so often, for example to say:

`You might just as well say,' added the Dormouse, who seemed to be talking in his sleep, that "I breathe when I sleep" is the same thing as "I sleep when I breathe"!'

He also tells a story about three young sisters who live in a treacle well, live on treacle, and draw pictures of things beginning with M, such as mousetraps, memory and muchness.

He later appears, equally sleepy, at the Knave of Hearts' trial and voices resentment at Alice for growing, and his last interaction with any character is his being "suppressed" (amongst other things) by the Queen for shouting out that tarts are made of treacle.
Given a reference text about the Dormouse, in which novel is it a character?
The Dormouse is a character in the novel "Alice's Adventures in Wonderland".