In an alternate BTVS world, when Angelus got cursed with a soul, and Spike got cursed with along him. So the two end up traveling together, becoming demon hunters--because Spike thinks they should do more of their new existence than to wallow in self pity. Angel is proud of Spike for how the younger vampire is able to adapt to their new existence so quickly. Later, this little admiration turns into slight obsession because now Angel views Spike as his beloved little brother who so awesome and smart and all other positive adjectives.

Spike is annoyed by this, but sort of likes that Angelus now doesn't despise his very existence. The two go through the century doing good and such.

Of course, years later, while in an assignment in LA to stop a demon cult, Whistler in lists Angel's help to assist the new Slayer. Angel initially disagrees but later accepts the mission because he remembers how Spike likes helping Slayers and maybe if he helped this one, Spike might turn up again and they could work together again!

Then he meets Buffy and immediately thinks that she's perfect for his little brother. She's sassy and snarky like Spike and so full of life. So wouldn't it be great if she were to end up with his little Willy?

Anyway, throughout S1, Angel keeps telling Buffy about his cool, smart and amazing little brother in hopes that she'd actually start liking Spike back. Of course, it does the opposite because she feels that Angel is trying to hook her up with this geeky loser little brother, which is something she doesn't want. Let's just say, Angel usually regale her with William's amazing poetry skills and other more brainy abilities than his actual skill as a warrior.

Anyway, cue in S2 when Spike rolls into town to check up on Angel and Buffy's eyes widened because the hot vampire was so far from how she pictured William to be. Why didn't Angel tell her his little brother was drop dead handsome?

What happens next is up to you. Just liked the idea of Angel and Buffy having this sort of convo.

Buffy: Why didn't you tell me your little brother was hot?!

Angel: What are you talking about? I did tell you he was attractive smart and such.

Buffy: No, you kept describing to me a weird creepy nerd, not Adonis with brains!