what is a fanlisting?

Well, it is exactly as it sounds, a listing of fans of a certain theme. In this case it is a fanlisting for the relationship between the actresses Piper Perabo and Lena Headey. For more information please see The Fanlistings Network.

practically twins ?

The name comes from Imagine Me & You, when Luce finds out Rachels birthday is close to hers she says they're, "Practically twins."