Spike suspects Giles is his father (because they're both British and Giles feels a gut-wrenching disappointment towards him), Anya assumes she is getting married to Giles (because she is wearing an engagement ring and they jointly own the magic shop) and Willow and Xander think they are a couple (because they woke up next to each other and Willow is wearing his jacket). Giles, Anya, Xander, Willow and Tara figure out their names from their IDs and Dawn's from her necklace.
Willow
Tara