Wesley and Cordelia try to catalog Angel's relationships.
I've been rewatching AtS, and I was intrigued by Fred and Gunn's exchange in Offspring when pregnant Darla shows up:
FRED: Who's Darla?
GUNN: Angel's old flame from way back.
FRED: Not the one that died?
GUNN: Yeah. No, not that one. The other one that died and came back to life. She's a vampire.
FRED: Y'all have a chart or something?
GUNN: In the files. I'll get it for you later.
I got curious as to what that chart looked like, so...I made one up. The original was begun by Wesley some time during the second season of AtS, and was continued after their return from Pylea. Cordelia added her own notes during the middle of S3, which is the last time it was updated. (Angel found the file around that time and confiscated it in a fit of pique.)