D&D One Shot

The characters are all part of the same crew of a ship who must slay a honorable lair. Two of the characters have fallen in love.
It is at an isolated circus which is near to a mordenkainen's magnificent mansion.
There are a family of mismatched renegades sitting on a deep pool with something shiny. And a veteran wants to make a gnomish suit of armour.
At some point they find a written note.
As the adventure progresses a portal slowly starts to open

The PCs are feared leaders of a cult who must create a safe place for a sacrificial tailsman. One or more characters is currently cursed. It might involve winter.
There is a desperate ruler who tries to help them.
The characters start during an attempted escape. Partway through they spot foes who are unaware of them. If things get stuck they discover an unexpected place to rest.
It finishes with a newborn or child on the way. Possible sequel... a clue from a reward or treasure points to an infamous dungeon...

The PCs are mercenary bards who must find a buyer for an enchanted key. Two of the characters have a bet about the evening. It might involve lycanthropes.
There is a shapechanging politician who wants to do the same thing. they are the childhood friend of a character.
The characters start running away from something. Early on foes are waiting for them. If things are going nowhere it starts to rain.
It finishes with someone imprisoned. Possible sequel... a character's homeland is under threat

The PCs are all part of the same crew of a ship who must capture a repulsive treehouse. The mood might be... tense
There is a young alchemist who tries to help them. they share a passion with a character.
The characters start with an explosion. Partway through an ally turns out to be an enemy. If things slow down something betrays them.
At the end there is a reward of a noble title. Possible sequel... an NPC from the adventure hires the characters for something totally different

The PCs are fun-loving criminals who must slay the Tarrasque. A character is accompanied by an annoying friend. It might involve dragons.
There is a brash troll who has important information for them.
The characters start during a heist. Early on they encounter local authorities. If things are going nowhere they uncover a secret stockpile.
At the end there is the characters splitting up treasure. Possible sequel... the adventure becomes the first of a multi-part quest around the same theme