One popular Buffy centered crossover fanfiction is the one where she crosses over with the 'Supernatural' universe. It combines the demon - hunting elements of both shows in an exciting way. Another good one is the crossover with 'Doctor Who'. The Time Lord's adventures blend well with Buffy's fight against the forces of darkness in Sunnydale.
First, you need to have a good understanding of the Buffy universe. Know the characters, their personalities, and the rules of the Buffy - verse, like how vampires are staked. Then, choose the other universe you want to cross it with. Decide on the main plot points that will bring these two universes together. For example, if it's a crossover with 'The X - Files', you could have a plot where a demon is causing strange occurrences that Mulder and Scully are investigating, and Buffy gets involved.
One great Buffy and Charmed crossover fanfiction is 'The Power of Two Worlds'. It combines the unique magic systems of both shows in an interesting way. The characters from Buffy and Charmed have to team up to fight a common enemy that threatens both their universes. The author does a good job of keeping the personalities of the original characters intact.
I really liked 'When Hunters Meet Slayers'. It's a well - written fanfic that does a good job of melding the two universes. It has some great action scenes where Sam uses his research skills to help Buffy and her gang figure out a new type of demon that has emerged, which is a combination of a demon from 'Supernatural' and one from 'Buffy'.
There's also 'Bones Meets Buffy'. In this fanfic, the two universes collide when a series of murders in Buffy's Sunnydale seem to have a connection to some archaeological finds that Bones is researching. It's a fast - paced story that keeps you on your toes. The author does a good job of maintaining the personalities of both sets of characters. For example, Bones is as logical and matter - of - fact as ever, while Buffy is her brave and sassy self.
A popular one is 'Crossing Paths'. This fanfiction has an interesting take on the crossover. It starts with a mystery that involves both the Supernatural and Buffy universes. The author does a great job of writing the characters true to their original personalities. Buffy's determination and the Winchesters' tough - guy attitudes are on full display, and the story builds up to a very satisfying climax.
A common theme is the rekindling of their relationship. Whether it's a romantic or a platonic bond, it often focuses on how they reconnect. Another theme is the fight against a greater evil. Since both are from the Buffyverse which is full of demons and dark forces, this is a natural theme.
One great 'angel and buffy crossover fanfiction' is 'Crossed Paths'. It beautifully weaves their two worlds together, exploring their complex relationship in a new and exciting way. Another one could be 'Reunion' which focuses on how they handle a new threat together after being apart for a while.
She could fit in as a specialist in the supernatural. The Avengers often deal with high - tech threats, but Buffy's expertise in the world of demons and magic would be a fresh addition. She could be the one to handle the more 'creepy - crawly' threats that the Avengers might not be fully equipped for.
Love and sacrifice are common themes. Their relationship has always been about love in different forms and often one has to sacrifice for the other. So in crossovers, this is often explored further.