Well, the wedding guest is an important part of the story. He was just about to enter the wedding when the mariner grabbed his attention. The mariner had this intense look in his eyes and started to narrate his journey. The wedding guest had no choice but to listen. His journey was full of hardships after shooting the albatross. All the crew members suffered and the wedding guest was made to experience all this through the mariner's words. In the end, the wedding guest is left with a different perspective on life and the consequences of one's actions.
The key element is the interruption of the wedding guest's journey to the wedding by the ancient mariner. Another is the mariner's tale which includes the fateful shooting of the albatross. Also, the supernatural events on the ship like the strange apparitions and the curse that befell the crew are important elements.
One horror story is when a guest got extremely drunk and started making inappropriate toasts. He slurred his words and told embarrassing stories about the bride from their childhood that she didn't want shared. It really put a damper on the mood.
A wedding guest once gave a speech full of offensive jokes that made everyone uncomfortable. It was supposed to be a happy occasion, but that speech just turned the whole atmosphere sour.
Sure. There was a guest who brought a really noisy and unruly child. The child ran around during the ceremony, screaming and knocking things over. It was so distracting for everyone. The parents didn't seem to care much about controlling the kid.
An unexpected guest could be a human who has some sort of special ability to see the supernatural world but has been hiding it. This person could come forward at the wedding and reveal that they know all about the vampires and werewolves and that they have a message from a higher power about Jacob and Bella's relationship. It would be very unexpected as no one expected a normal human to be involved in such a way.
One horror story could be a wedding guest who showed up in a completely inappropriate white dress, trying to upstage the bride. It was really disrespectful and made the bride very upset.
One factor is fashion trends. If a certain hairstyle is popular in the fashion world, like the messy bun which has been trendy lately, girls are more likely to adopt it.
Perhaps Neville's grandmother Augusta. She has always been a bit of a stern character, and at first, no one expects her to come. But she shows up with a beautiful family heirloom as a gift for Ginny. She might even give a short but heartfelt speech about how she has watched Harry grow and how proud she is of the young couple. This would be unexpected as she doesn't seem the type to be very involved in the social lives of the younger generation.