Alyx's Mother
I just finished "Half-Life 2: Episode 2" and I noticed something. Befor the fight to defend the missle silo, Eli walks over and picks up a picture of himself with Alyx as a child and his wife. After he put the picture down I took a closer look at it. now I could be wrong, but the woman in the photo that is Eli's wife looks a bit like the character you play in "Portal" If it is this would be a good way to link the two games.