"Hilaristurbing" (adj) used to describe something that is both HILARious and dISTURBING.
It's origin is from an online story written by Alexandra Erin called "Tales of MU".
In the story - an adventurous nymph named Amaranth describes her attempt to teach a horse to count with the intent to avoid her deity's prohibition against lying with unintelligent beings. Chapter 60 - Leather
“Hey, I just discovered a new adjective,” Steff said. “‘Hilaristurbing’.” She turned to me. “I think Amaranth has exited the dungeon, hon…”
Where, if you hate someone, nothing they say will be funny to you, no matter how funny it actually is. Additionally, when you like someone, every little thing they say is funny no matter how stupid it actually is.
James- Hey guys look! (makes unfunny face)
Hilary- Hahaha! James you're so funny!
Hank- Man Hilary must really have Conditional Hilarity Syndrome because that was the least funny thing anyone has ever done on planet earth.
From the days of newspaper TV Guides that would write two sentence synopses (loglines) of a television show. Sometimes these summaries wouldn't sound comedic on the surface, so "hilarity ensues" was used to ensure the audience understood it was a premise for a comedy.
Tonight on Seinfeld, George decides the best time to have a snack is during sex. Hilarity ensues.