For those times when you go "You *finally* arrive in Small Town #3. After a bit of asking around, you find out that there's a sale on cheese, the sewers are infested with giant hungry weasels, and the locals are planning a wedding" and the players go "Sweet! We crash it!"
1. An important alliance between two nobles.
2. A secret marriage between two nobles, who's parents will be some degree of unhappy when they find out.
3. A secret marriage between a noble and a commoner. The noble's parents will be extremely displeased when they find out; the noble was supposed to marry someone important to end some war or another.
4. The bride is a werewolf!
5. The groom is a vampire!
6. Part of an important rite for a weird local fertility cult. The human sacrifice is purely metaphorical.
7. Part of an important rite for a weird local fertility cult. The human sacrifice is very much not metaphorical, and the bride and/or groom is it.
8. Part of an important rite for a weird local fertility cult. They still need a human sacrifice -- preferably one from outside the community.
9. The bride and/or groom is under the effect of a charm effect. It will wear off at the worst possible moment.
10. The bridge/groom has been, or is about to be, kidnapped by nixies/satyrs.
11. The bride/groom gets cold feet.
12. The bride/groom gets cold feet. S/he makes it look like s/he's been kidnapped by nixies/satyrs.
13. The bride/groom gets cold feet. S/he gets the other one kidnapped by nixies/satyrs.
14. The couple is already bickering constantly. It's starting to get on everyone's nerves.
15. The couple is madly in love, utterly normal, and deeply obnoxious.
16. The bride/groom is a doppelganger.
17. The bride *and* the groom are doppelgangers. Neither is aware that the other one is one.
18. The bridge/groom is a secretly a hideous monster! The wedding is all just a convenient pretext to get a large number of people in one room for convenient mid-rampage snacking.
19. The bride/groom is not whom s/he appears to be. S/he's actually an obsessive stalker, and has kidnapped the real bride/groom to take his/her place for the ceremony.
20. The couple has made a poor choice of flower arranger. Odds are good that the ceremony is attacked by angry sentient plants.