With what creatures of fantasy is Pearl is continually compared?

"Ay, indeed!" cried good old Mr. Wilson. "What little bird of scarlet plumage may this be? Methinks I have seen just such figures, when the sun has been shining through a richly painted window, and tracing out the golden and crimson images across the floor. But that was in the old land. Prithee, young one, who art thou, and what has ailed thy mother to bedizen thee in this strange fashion? Art thou a Christian child,--ha? Dost know thy catechism? Or art thou one of those naughty elfs or fairies, whom we thought to have left behind us, with other relics of Papistry, in merry old England?""