Epileptic Trees: Ford exhibiting some brass balls and asking about his "reward", to Spike and Dru blankly stare back. There's some debate as to who did the actual siring, but from the way she slowly opened her eyes in response to Ford's question, and the fact that she hadn't gotten a "treat" yet, Drusilla's a good bet.
Harsher in Hindsight: The ending of the episode is an in-universe example. Depressing and sad when aired, but the characters hadn't suffered great tragedy or major deaths yet. By the time the show is over that ending is second only to "The Body " in tear factor.
Moral Event Horizon: If Ford wasn't over it just by helping to mastermind the whole vampire pact, he's definitely over it when he knocks Buffy down the stairs while she tries to reason with the other clubgoers. Of course, as Buffy points out, he wanted to be the villain - it just made the whole death wish easier for him.
You can see Beljoxa's Eye on a mural behind Billy and Buffy. Beljoxa's Eye plays a pivotal role in season seven's "Showtime".
How much the Buffyverse would have changed if Drusilla had simply taken Angel's advice here. Angel wouldn't have lost his soul in "Innocence", and might not have departed for L.A. the following year. Spike ended up having to help Buffy kill Angelus in "Becoming, Part 2" which caused Drusilla to dump him; That event led to Spike's entire personal transformation and turgid affair with Buffy. Drusilla later turned up on Angel to sire Darla as a vampire again, thus leading to Darla's one-night stand with Angel and culminating in Connor's birth. Phew.