Wesley points out that "A father doesn't have to be possessed to terrorize his children." This one of the earliest hints at Wesley's issues with his own father.
The nun at the church seems to immediately know that Angel is a vampire. This is the only time we see anyone of the church to be aware of vampires (other than Caleb) and possess this ability.
This episode marks the second instance of a human being fully or partially soulless; the first was Buffy in Living Conditions (1999).
Just as he indicates to Cordelia at the end of Somnambulist (2000) Angel here tells Wesley that being prepared to kill him if he turns evil again is a good thing.
Angel and Wesley each seem to possess a double-bladed Bavarian fighting axe. Cordelia asks Buffy about Angel's in I Will Remember You (1999) when, believing Angel Investigations is closing its doors forever, she begins tagging items for inventory. Wesley brings his new one into the office in "Expecting," prompting Cordelia's friend Serena to remark, "nice ax."