|Series||The Grim Adventures of Billy & Mandy|
|Writer|| James Silverman
|Cartoon Network US Premiere||March 21, 2006|
|Paired with||Herbicidal Maniac|
A Grim Day
Chaos Theory is the second episode from the sixth episode from season five of The Grim Adventures of Billy & Mandy.
Ever since Hoss started dating Eris, anytime Hoss or anyone near him makes damage, it's reverses back to it's original state. Now Billy, Mandy, Grim and Irwin must get Eris to dump him if they want to get Hoss' old life back and for everything in the world will go back to order.
- Story by: James Silverman and Mike Diederich
- Storyboard by: Mike Diederich
- Directed by: Eddy Houchins
Grim, Billy, Harold, and Mandy go to CostMo. Mandy and Grim notice something different, Costmo is usually crowded and full of Chaos now it's the opposite. Just then Hoss Delgado crashes through the roof. Hoss says it was on his list (which it was) suddenly the shattered glass go back to the ceiling and repairs it self.
Meanwhile, Billy meets up with Irwin and the same thing happens to them when the balls they let out go back inside the cage. They go inside a mayonnaise jar where they "moisturize". Hoss mistakes them for ghost and fires at the before Mandy stop him. The same thing happens again.
Hoss explains that when Eris' life went orderly, his went too. Eris has also been ruining his life too; by redecorating his room, destroying his old photos, organizing his socks, and tampering with his wardrobe. Mandy points out that Hoss needs to break up if he wants his old life back, but Hoss admits that he's afraid to do so, pointing out that she probably won't take it that well and explaining that she "gets really freaky" when she's mad. Grim offers to do it for him while Hoss goes and cowers in Aisle 5, but Eris turns into a demon and scares Grim. Mandy also tries, this time by imitating two gossiping women talking about they saw Hoss flirting with an attractive redhead in Aisle 5. But seeing her mad makes Hoss love her more, Eris apologizes before transforming into a bug and eating Hoss again. Hoss gives up, but Mandy will not allow it.
Irwin and Billy (poorly) disguise themselves as a grown man to distract Eris only for them to ruin it. Eris levitates Billy by asking him what's he up to. Billy tells her what's going on which prompts her to shrink him into a small colony of Billys. Eris yells for Hoss and flirting won't work this time. Hoss finally confesses about wanting to break up with Eris, for a couple of reasons: He wants to fight monsters again and Eris isn't the same "crazy, goddess [he] fell in love with. [She's], like, normal." Angered by the last comment he made, Eris turns into a giant bug and eats Hoss again.
- The store, CostMo, is a parody of Costco.
- This episode marks Eris's final appearance in the series (other than her cameo in Grim's flashback in Wrath of the Spider Queen) before eventually returning in the unmade Underfist series, in which she splits into two different versions of herself, Nice Eris and Naughty Eris, as a result from being heartbroken from her breakup with Hoss.
- On the subject of that matter, in Underfist, Hoss is said to have fallen into depression after the break up. This contradicts his other appearances after the breakup, as he was perfectly okay with it.