Willow uses a spell that supposed to bring weapons to Buffy to help defeat Glory. She inadvertently makes Buffy a magnet for alternate versions of herself to come to their dimension. One thing seems to a pattern for all the Buffys from the different realities - they are all in a relationship with Spike.  

kudos/optional:

1. if you have  scene where all the Buffys look at original Buffy in pity because she's the only one not getting some from Spike.

2. if there's a Buffy who has lost her Spike.