Mrs. Which is one of the characters of the A Wrinkle In Time novel.
In the book, her physical appearance is not set; she appears as a shimmering light most of the time. However, she does once take on the appearance of a traditional witch, complete with black hat and broom. She does not stay long in this form, though, as corporeal appearance is quite difficult for her to maintain. She first appears at the end of Chapter 3. She is the wisest of, and the clear leader of the three women, and upon appearing, immediately demonstrates her vast knowledge of understanding in tesseract travel. Her distinguishing quirk is her long, drawn-out method of speech, symbolized by doubled and tripled consonants in her words (as in; "Nnoww, cchilldrenn, yyou musstt nott bee frrightennedd att whatt iss ggoingg tto hhappenn,"). She is the one who usually provides the group, most especially Meg, with the clues the children need to solve the problems encountered during their travels.