Exactly what the title says (One-Shot)

Crack and comedy alert!

When Obi-Wan told Luke his father had been betrayed and murdered by Darth Vader, he didn't realize that a confused, fresh-out-of-time-travel Anakin Skywalker was scratching his head and standing behind him.

Anakin demands to know this guy's pre-Sith name. Luke is just starry eyed over his father. Obi-Wan wants to blink out of existance right there.

And then he accidentally becomes the reason the Empire rose to power.