
John Wick- With a price on his head and blood on his hands, John Wick has gone into hiding. Constantly watching his back for the denizens of the underworld who would have his head, John’s “retirement” has become an exercise in futility and he knows, eventually, the sins of the past will catch up with him.
One night, while searching for camp in the wilderness, he was visited by a shimmering figure. She spoke of a catastrophic event that loomed on the horizon. A story of man, gods, and shattered realities. None of this interested John, until the being spoke of a timeline in which his departed wife still walked the earth. A timeline that was skewed by a desperate god trying to alter destiny.
John was offered an opportunity...an impossible task. Find the god known as Raiden and kill him. Do this and the timelines will merge and he will be reunited with his lost love. Imbued with divine strength by the being, John would once again be pulled into a life he loathes, but for another chance to hold his darling Helen, he would gladly walk through the gates of hell. To find a way to kill a god...he just might have to.
May add a few later. So, how would you write a guest character into the story.
Predator:
Exiled from his home planet as a Bad Blood and stranded in outworld (I am not clear on how this realm thing works. Vogel told me that it was explained to him by Tobias as them simply being other planets. Doesn't really make sense but whatever. The guy clearly doesn't put that much thought into the lore these days so why should I?)
Has been there for a couple hundred years and in that time became a respected war lord, ruler and ally of the great emperor Shao Kahn. So basically A Predator with samurai armor, spring activated wrist blades and such.

Ash Williams is hanging out in an RV, drinking and smoking with a woman he met at a bar when the wind starts howling outside. Suddenly something start's banging on the front door.
Ash: "S***, someone must have found that goddamn book!!"
The door flings open, and in steps ... Fujin.
Fujin: "Greetings Ash, you have been chosen to defend Earthrealm from it's greatest threat yet. You must come with me."
Ash: "Excuse me, but who the f*** are you!? And can't you see that me and the nice lady are a busy at the moment?"
Ash glances at his date, only to find that she has transformed into a Deadite.
Ash: "Goddammit, nevermind just help me kill this thing!"
Fujin quickly kills the Deadite.
Fujin: "I am Fujin, god of wind. Get your weapons and I will open a portal so we may join the rest of the Earthrealm warriors."
Ash: "Warrior? You must have me mixed up with someone else grandpa, but wherever you're taking me is probably safer than sitting here waiting for the next Deadite to show up."


There is no preferred guest character.

The only good guest is a dead guest!
Wait... that doesn't work in this franchise... everyone dies.
The only good guest is a non-existent guest!