Corrected entry: In the episode 'Selfless' Anya has a flashback to a song she sang at the time of the episode 'Once More, With Feeling'. During this flashback her hair is much longer and a much harsher blonde than it actually was during that episode.
Corrected entry: In "Selfless", Anyanka is quite strong and holds her own against Buffy for quite a while. In previous episodes ("The Wish" and "Two To Go (1)" to be precise) Anyanka has had nowhere near this level of strength.
Correction: Anya has been closely involved with the gang for a number of years by this point. She's fought next to Buffy countless times. It can be taken for granted that she knows Buffy's fighting style and methods. She may not be any stronger, but she knows how to anticipate Buffy's attacks.
Corrected entry: In 'Selfless' Anya wants to reverse her wish that killed 12 people and is unable to do it, but during 'The Wish' we were told that all you have to do is destroy her power source and all her wishes will be reversed (Anya has to have a power centre - we see in the episode 'Older And Far Away' that ALL vengeance demons have one). Even though the gang don't know this any more (they wouldn't have any memory of researching it), surely Anyanka herself would know her own weakness?
Correction: First, Anya may not want to destroy her power center because it would reverse every wish she ever granted, not just the most recent one. Second, breaking the power center would also make Anya a human. The point of the episode is that Anya has to learn to live in her own way and pay for her decisions, and to this end she believes that D'Hoffryn killing her would be justice. Asking D'Hoffryn to reverse The Wish is the only way for the developing character to resolve the conflict.
Corrected entry: In the season 3 episode "Doppelgangland", which originally aired in 1999, Anya told a barman that she was 1120. This would mean she was born in 879 AD. But in the season 7 episode "Selfless", a flashback to 880 AD showed her as a young woman (about 20). She should've only been one year old.
Correction: In the same way that vampires mark their ages from their 'conversion', Anya might be calculating her age from when she became a vengeance demon.
Correction: It's a flashback. There are many other examples in film and television where a character's flashback does not accuratetly reflect the actual events that took place. It is a vision of that character's memory, and is therefore subject to various inaccuracies.
Phixius ★