Alice's Adventures in Wonderland and Through the Looking-Glass
How we cite our quotes:
She generally gave herself very good advice (though she very seldom followed it), and sometimes she scolded herself so severely as to bring tears to her eyes; and once she remembered trying to box her own ears for having cheated herself in a game of croquet she was playing against herself, for this curious child was very fond of pretending to be two people. (Wonderland 1.21)
Early in the Alice books, we learn that Alice seems to have several personalities swirling around inside her. It's easy for her to pretend to be more than one person, to see both sides of an argument, and to get lost in the roles she's playing.
"I wonder if I've been changed in the night? Let me think: was I the same when I got up this morning? I almost think I can remember feeling a little different. But if I'm not the same, the next question is 'Who in the world am I?' Ah, that's the great puzzle!" (Wonderland 2.7)
The joke, of course, is that Alice wasn't the same when she got up this morning. Everyone is a little different every morning than they were the day before, and for a growing child the change is even more obvious. This creates a crisis for Alice – if she's not the same person she used to be, does that mean she's losing her identity?
"No, I've made up my mind about it: if I'm Mabel, I'll stay down here! It'll be no use their putting their heads down and saying 'Come up again, dear!' I shall only look up and say, 'Who am I, then? Tell me that first, and then, if I like being that person, I'll come up: if not, I'll stay down here till I'm somebody else.'" (Wonderland 2.9)
Wonderland is a place of fluctuation and change. Alice determines to let her identity keep shifting until she's happy with it, and only then to return to the "real world" where identity is static.