It is well-established that though a vampire possesses a heart, it does not pump and, accordingly, does not circulate blood through the vampire’s vestigial circulatory system. (Recall in the …

A discrepancy (and not the last!) in vampire mythology is shown at the beginning of 1.05 Never Kill A Boy On The First Date. When Buffy stakes a vampire, he leaves …

In 1.07 Bachelor Party, Angel does not realize Richard is a demon until he sees him change at the restaurant. However, Angel can smell the difference between humans and demons. …

Lyssa was interrupted before successfully opening the Seal of Danthalzar in 7.14 First Date. Two episodes later, the seal is closed by Andrew’s tears. It wasn’t until 7.22 Chosen that …

In 1.11 Out Of Mind, Out Of Sight, Angel saves Giles, Xander and Willow by turning off a leaky gas valve. He tells them:

“It’s not like I need the oxygen.”

This …

In vampire mythology (and the Whedonverse), a vampire cannot enter a person’s home unless it has been invited. This is first seen in the Buffy episode 1.07 Angel:
Angel: “It’s all right. …

You can clearly hear Angel breathing heavily when he runs over to Buffy in 1.12 Prophecy Girl, but he then says he can’t resuscitate her as he has no breath. He …

Angel’s reflection is briefly seen in a frame in Buffy’s room in 2.09 What’s My Line? (Part One), above the blue light.

When Angel uses the phone in 3.22 Graduation Day (Part Two), you can see the reflection of his fingers and his shirt in the chrome plating of the phone.

As Angel pulls the Mayor off Buffy in the hospital in 3.22 Graduation Day (Part Two), you can briefly see his reflection in the glass of the room’s door.

Vampires are supposed to have excellent vision so why does the vampire Dalton need glasses?

Vampires are supposed to have heightened hearing capabilities so why can’t Spike hear the nerds discussing their plans for the Slayer in 6.09 Smashed? He’s only standing a few feet away. …

In 1.01 Welcome To The Hellmouth, Darla’s bitemarks on the dead boy run horizontally. It would be impossible for Darla to have positioned her head to get bitemarks like this.

When Spike is walking down the school hallway in 2.03 School Hard, you can briefly see his reflection on the lockers to the right.

Spike’s reflection can be seen multiple times in Giles’ glass bookcase in 4.09 Something Blue.

In the season two episode 2.03 School Hard, Spike says Angel was his sire, which we discover was actually Drusilla in a flashback during the episode 5.07 Fool For Love. The term …

With his vampire strength, Angel should easily be able to smash through the tiny padlock which is locking him in the cage in 2.09 What’s My Line? (Part One) - but …

We know that vampires can’t breath but when Angel first comes out of his grave in 1.15 The Prodigal, we can see both his and Darla’s breath in the cold air.

How could Angel get an erection? Surely vampires have no heart beat, therefore no blood flow, therefore they can’t get erections.

As Buffy is fighting the newly-risen vampires in the basement in 7.08 Sleeper, she stakes the vamp in the blue shirt on the wrong side of his chest.