We can't get enough of Oprah.
Er...we mean, Mrs. Which.
Mrs. Which seems the least material but the most powerful of the three Mrs. Ws. She also seems to be the most distant from human reality: she's the one who forgets that humans need three dimensions to live and tries to land them on a 2-D planet. Her voice is represented with llotts of ddoubbled lletttters, suggesting that it sounds kind of echoey, or like it's coming from a long way off.
Despite Mrs. Which's strangeness, Meg feels that she is "someone in whom one could put complete trust" (4.41); while she's not as immediately friendly as Mrs. Whatsit, it's obvious that she cares deeply about fighting the good fight.
At the same time, she's not above making a joke: at one point she appears decked out in classic Halloween witch's finery, complete with broomstick, which forms both a pun on her name ("which"/"witch") and a visual rhyme with Mrs. Who's quoting of lines from the Three Witches in Macbeth (oh look, Shakespeare again). Even when channeling the Wicked Witch of the West, Mrs. Which is always a force for good to be reckoned with.