An alternate universe where Oz never left the show (Buffy, Season 4) and Doyle never died. (Angel, Season one.)
When Buffy Summers dies giving birth to Parker Abrams' child, Angel just has to show up, even if Buffy doesn't know he's there. So when she names the baby girl Angela, it's the final straw.
Years have passed and Angela has just celebrated her sixteenth birthday when a mysterious man comes to tell her something, and her whole world changes.