James Marsters (Spike) has revealed in interviews that he played Spike having an attraction to Buffy from the start, which is evident in the scene where he observes Buffy for the first time, on the dance floor at the Bronze.
Juliet Landau didn't have to audition for the part of Drusilla. Joss Whedon had been very taken by her performance in Ed Wood (1994) so she was offered the part within an hour of meeting with Whedon.
Despite, or because of, Joyce's attack on him, Spike later has a deep respect for Joyce Summers, developing somewhat of a friendship with her.
Principal Snyder talks to a cop after the fight, and they agree to say what happened was another "gang related violence," indicating that the Sunnydale police have been covering up vampire attacks for a while now.
Spike calls Angel his sire, an intentional misdirection to make fans believe that Angel was the vampire who sired him. When Spike uses sire he also mentions "Yoda", indicating that he thought of Angel as his mentor - the father-figure who taught him after he became a vampire. In interviews, Joss Whedon has stated that a "sire" can mean any vampire ancestor. So Spike can consider Drusilla, Angel, Darla, and the Master to all be his sires, even though he was sired by Dru.