Trivia: With this episode, David Boreanaz is the only remaining original cast member from season one. Glenn Quinn's character died in episode 9 (He died in real life 3 years later) , Charisma Carpenter was written out of the show at the end of season four, while Alexis Denisof and J. August Richards began as guest stars; Amy Acker and Andy Hallett weren't introduced until season two, and Vincent Kartheiser first appeared in season three.
Trivia: Joss Whedon wanted Sarah Michelle Gellar to guest star as Buffy in "You're Welcome" (the show's 100th episode) and "Power Play" (the penultimate episode), but she was unavailable. She later became available for the series finale, but Whedon declined, wanting the series to end focused on Angel. Conversely, David Boreanaz was available for the Buffy finale, but only for a limited amount of time.
Trivia: Angel's plan to kill the ranking members of the Circle of the Black Thorn bears a striking similarity to the mass murders ordered by Michael Corleone in the climax of The Godfather and its sequels.
Trivia: When the gang are in Spike's apartment where Angel is assigning them to go after members of the Circle of the Black Thorn, Spike says "First off, I'm not wearing any amulets. No bracelets, broaches, beads, pendants, pins, or rings. " This is a reference to how Spike dies in the series finale of Buffy by wearing an amulet to destroy the Hellmouth.
Trivia: During the season's Angelus arc, a lot of David Boreanaz's dialogue was improvised.
The Cautionary Tale Of Numero Cinco - S5-E6
Trivia: When Carlos flies through the air after being attacked at the start of the episode, he emits a Wilhelm scream.
Answer: Due to his epiphany, Angel basically had the 'true darkness' he worked so hard to reattain ripped away from him, like his soul was after sleeping with Buffy.