"Because I'm sick of everyone and their aunt Trixie always taking me scythe! And together, using the Bone of Barnacles, we can fight the Delightful Children and Mandy. I'll get me scythe, and you'll get your friends back."
Grim is often stuck with cleaning-up the consequences of mishaps that are in no small part due to Billy's stupidity and lack of common sense. On Mandy's part, Grim is often forced to do her chores and obey her direct orders, as her unwilling slave. In several times in his own series that he does the dishes every single day for Billy and Mandy since they first met which he seriously despises.
The Grim Adventures of the Kids Next Door
As Numbuh 1 is disguised as Billy whilst the rest of the Sector V try to get Billy's lucky pants off from him, Grim comes to Billy's house, and mistakes Numbuh 1 for Billy. In a sudden show of pain by using the Bone of Barnacles, Grim senses that his scythe has been fused with evil and strangely delightful children, and Numbuh 1 realizes that he is talking about The Delightful Children From Down The Lane. The Delightful Reaper begins fusing kids into it, including Numbuh 2.
Shortly after Mandy was disguised as Numbuh 1 and changed KND into her organisation, so only, becoming the leader of the MND. On the way to the Moonbase, Numbuh 1 and Grim are attacked by Numbuh 60 in which they are in restricted airspace but doesn't realize its Numbuh 1, Numbuh 1 and Grim arrive at the Moonbase, where Grim finds out that Numbuh 1 isn't Billy, and Mandy imprisons them.
The Delightful Reaper continues fusing with children, so after escaping, Numbuh 1 and Grim fuse together with the Bone of Barnacles to create a Giant Skeleton Samurai to battle the Delightful Reaper after Numbuh 5 free them. A giant M.A.N.D.R.O.B.O.T. piloted by Mandy, Numbuh 3, and Numbuh 4, comes into the battle. Mandy's robot begins to lose until Numbuh 1 and Grim show up and fight the Delightful Reaper, though they begin to lose as well because Billy's dad, Harold's lucky pants are impervious to lasers, supernatural energy, and mustard.
When the Delightful Reaper is distracted by Numbuh 1 and Grim, Mandy purposely fuses herself with the Delightful Reaper, giving her control of it. However, Harold comes, removes the lucky pants and takes them away, being really, really angry that someone is wearing his pants. Without the lucky pants, the Delightful Reaper is defenseless and the Skeleton Samurai finishes it off, freeing the other kids inside it. Mandy is taken away by the KND, but eventually she escapes, vowing revenge.
- Grim's voice actor is Greg Eagles in the series, but in Cartoon Network: Punch Time Explosion, it is Neil Kaplan.