In Killed By Death, when Buffy snaps Der Kindestod’s neck his hat fall of his hat and onto the pipe behind him (38:53 approx) but in the next shot the hat seems to have disappeared.

In Conversations with Dead People, the First wreaks havoc on the Summers house. In amongst the chaos and terror, suddenly we glimpse all the kitchen chairs have been stacked on the kitchen table. This is a visual reference to the classic horror film Poltergeist, in which a young girl is …

In Bewitched, Bothered and Bewildered, when Giles is doing the spell with Amy to cancel Xander’s love spell, 38:34, we can clearly see a string attached to Giles’ cravat, in the right side of the screen near a balcony.

In a Halloween episode of British TV soap Eastenders, Lynne Slater dressed up as Buffy for a party at Angie’s Den.

In the episode Never Kill A Boy On the First Date, we hear the music “Rotten Apple” by Three Day Wheely (from the album ‘Rubber Halo’) as Cordelia and Owen dance.

A trans-Neptunian object was named after Buffy? From Wikipedia:

2004 XR190 (also written 2004 XR190) is a newly discovered trans-Neptunian object located in the scattered disc. Astronomers led by Lynne Allen of the University of British Columbia made the discovery as part of the Legacy Survey using the Canada-France-Hawaii Telescope. The …

In the Angel episode Fredless, Cordelia and Wesley do an amusing re-enactment of Buffy and Angel’s relationship for Fred. It goes as follows:

Cordy: “Let me break it down for you, Fred.”
Cordy now pretends to be Buffy while Wesley is Angel.
Cordy: “Oh Angel! I know that I’m a Slayer and …

Throughout her fight with the Turok-Han, Buffy is wearing black trainers, but when she walks away from the ‘Thunderdrome’ (at 38.55) she’s wearing black, heeled boots.