The inscription on Buffy’s grave stone after she died in The Gift reads:
Buffy Anne Summers; 1981 - 2001; Beloved Sister; Devoted Friend; She saved the world; A lot.

Tom Kiesche, who played the vampire at the beginning of the episode The Gift, played Detective Broomfield in the Angel episode ‘The Shroud of Rahmon‘.

Spike worked out in The Weight of the World that Glory had worked a magic spell so that people who witnessed her turning into Ben instantly forgot what they saw:
“Oh, I get it. That’s very crafty. Glory’s worked the kind of mojo where anyone who sees her little presto-chango …

In The Weight of the World, Willow sees the scene from Intervention in which the First Slayer told Buffy that death was her gift. Willow recognises the Slayer from her dream in Restless.

In The Weight of the World, we discover that Ben has a small, bare room in Glory’s luxurious apartment.

Xander’s bedroom in his apartment has a poster which reads “There’s money in arc welding!”, seen in The Weight of the World.

Joyce and Hank Summers return in a false memory flashback in The Weight of the World. We see a scene where Buffy’s parents bring baby Dawn home for the first time. This is the first time Hank and Joyce have been seen together since When She Was Bad (though we …

In Spiral, Anya suggests cooking Spam in the Winnebago (”Who’s up for some tasty fried meat products?”). Spam is pressed meat in a can, favoured by British people during World War II.

In Spiral, Xander mentions the time Buffy used a rocket launcher to defeat The Judge in Innocence.

In Spiral, Buffy calls Ben with the phone number he gave her in I Was Made to Love You. Either she took the slip of pink paper with the number on with her, or has memorised the number.

Buffy says in Spiral, “We’re not going to win this with stakes or spells or pulling out some uranium power core,” referring to Primeval, in which she destroyed Adam by pulling his power core from his body.

Jack Donner, who played Glory’s cleric in Spiral, played Romulan Subcommander Tal in the original Star Trek and has appeared in The Adventures of Rocky & Bullwinkle, Stigmata, Roswell, Malcolm in the Middle, Charmed and Mission: Impossible.

Lily Knight, who played Glory’s minion Gronx, has also appeared in The Singing Detective, Secretary and Artificial Intelligence: AI.

Wade Williams, who played General Gregor in Spiral, has also been in Erin Brockovich, MDs, 24, Enterprise, Six Feet Under, Charmed, The X Files, Becker, Star Trek: Voyager and The Larry Sanders Show.

Karim Prince, who played Dante, a Knight of Byzantium, in Spiral has also appeared in Malcolm in the Middle (as Cadet Stanley), The Bold and the Beautiful (as Raymond), MTV’s Undressed (as Randall), and Mighty Morphin’ Power Rangers (as Cestro/Blue Alien Power Ranger).