Lexes said: Me no get joke. Someone care to explain?
Mokou, being a hourai, has the title 'hourai doll' because while she's a human, her body isn't that of a human. (In Japanese, 'ningyou' can mean both 'doll' and 'form of a human'.) But as you would know, Alice has a spellcard named 'Hourai doll', so this joke.
edit) Oh wow, this is my 1111th comment on Danbooru.:)