However, the term 'best friend' is used loosely. 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, all as her unwilling 'friend-slave'.
Originaly a resident of The Underworld, Grim is an 'Undead, talking magical skeleton', along with the rest of his family: So-far, Grim has been idenitfied as having a father, (named "Earl" in passing,) a mother, (also only named in passing as "Miriam",) a grandmother known simply as "Granny-Grim", and a Great Aunt called "Aunt Kali", (named for the Hindi Goddess of the same name). Neither of Grim's parents speak with a Jamaican accent like Grim does, in-fact only Granny-Grim has been heard speaking with a Jamaican accent.
Born and raised in the Underworld, Grim attended Doomsday Junior High School with supernatural entities and other characters of the show, such as Eris, Nergal and Boogey. Grim was unfortunate enough to be stuck as the favorite target of the school bully, Boogie, who enjoyed making the lives of the other students, (Grim in particular,) as miserable as possible. Grim played Underworld Little League as a child, and was also a member of the 'Dead Poets Club' during Junior High school, but, thanks to Boogie's antics, Grim was labelled with the nickname of "Wedgie Shakespeare" for the rest of school. In Billy and Mandy Save Christmas, Grim mentions that he went to College with Santa Claus.
Grim also has ownership of the original Hellhound, of Greek myth; a massive, three-headed 'Demon-Dog' called Cerberus. How Grim ever came to own Cerberus was never addressed during the series, but it was evident in Cerberus' debut that Grim couldn't control him, claiming that Cerberus, "didn't just eat [Grim's] homework, [Cerberus] also ate [Grim's Dad]", (though it was probably just an exaggeration on the script writer's part).
Growing up, Grim has considered Dracula his idol.
Grim's age is hard to pin down; in A Grim Prophecy, shows an account of how Grim became the 'Grim Reaper' depicts Grim's early childhood taking place during the time of Neanderthal Man, putting Grim's age at an estimated at around 137,000 years old. In Wrath of the Spider Queen, it was shown that he was in his preteens in around the same time period, and that dinosaurs and cavemen were around then, (which is historicaly inaccurate,) which supports the same timeline.
Grim's appearence stays true to the iconic image of the Grim Reaper; Grim is depicted in the series has an adult-sized 'undead, talking magical skeleton'. Grim is most often seen wearing a long black robe with a hood; the robes make him look thinner than he actually is.
Grim is also seen with his scythe, an object of power in the series and the source of most of Grim's powers.
Described by series creator Maxwell Atoms as 'cantankerous', Grim is unsatisfied being stuck as Billy and Mandy's 'best friend-slave'.
First and foremost, Grim loves his scythe and his job, and was once sent to anger management because he loves his job "a little too much". Grim enjoys Ice Cream and Chocolate, his favorite part of the newspapers are the obituaries and his favorite time of the year is "El Día de los Muertos"--it's the only day of the year that is dedicated solely to him. Grim also love to play Golf and Mini golf--he has an excellent golf-swing technique--as well as any sport that involves swinging a stick, such as Baseball. Grim favorite dance is The Skeleton Dance--but hates having to dance it with amateurs.
Grim admits that he used to play "that 'Stairway-to-Heaven' thing" back during high school and is very good at playing the guitar, (or bad depending on ones interpretation, seeing as when he once played 'Stairway to Heaven' out in the street, it sounded good, but it also tore down the surrounding neighborhood.) Grim played the lead guitar position for Sperg's garage band, Purple Filth, for their entry in the Endsville 'Battle of the Bands', (see Battle of the Bands).
Grim hates both Billy and Mandy and often fantasizes about their gruesome deaths, releasing him from their company. In Billy and Mandy's Big Boogey Adventure, Grim confirms that as much as he hates Billy and Mandy, his hatred of Boogie far overshadows his hatred of them, driving Grim to go through the "Cannibal Run" to get to the 'Left Hand of Horror' first before Boogie. Grim also reveals that Horror's Hand cannot effect him because he lives his worst nightmare everyday--being stuck with Billy and Mandy as their 'friend-slave'. Grim also keeps a voodoo doll of Billy in his trunk, (Brown Evil). But deep down Grim actually cares for both Billy and Mandy, which he shows in several episodes notably he seems to like being with Billy more than Mandy because of his more kindness towards him and treating him more like a friend than Mandy, who constantly bosses him around and treats him like a slave and servant. He challenges Nergal to a fight for Billy and Mandy's lives, tries to help Billy overcome his fear of clowns, and helps Mandy get her nerve back.
Other things that Grim hates are most old folk, health freaks, the community, community service, neighbors and new neighbors even more-so, false alarms while he's at work, anytime that Billy and Mandy mix his professional life with their personal life, and Grim hates it whenever Billy goes through his trunk or robe pockets and when Mandy makes him do her chores.
It appears that he has met a giant monster named Cragera.
- Eris - Grim had a crush on her early in the series, during her 'valley girl' phase.
- Atrocia - TV Horror show hostess, (parody of Elvira: Mistress of the Dark).
- Malaria - A Goth woman who Grim first met at a beach. She later freaked out when she found out that he was the real Grim Reaper.
- Velma Green(?) - former best friend, friendship renewed after events in Billy & Mandy: Wrath of the Spider Queen.
- Pinface's un-named sister - Used to be friends with her brother, Pinface, when they were kids, met her at the Netherworld Mall, but later broke up with her because her 'pinhead' bowling pins kept poking him in the eye whenever he tried to make out with her.
- Lubber - Not a romantic interest of Grim's per-say, but Grim was her love interest, she would follow him everywhere back at school and started to eat anyone who made fun of Grim, after eating most of the school's student body, Lubber was banished by the school principle to guard the 'secret of the universe'. She also trick everyone and then pushed Mindy so that she protects what she used to.
Grim is the Grim Reaper, a privlidged title, role and position within The Underworld. Armed with the Reaper's Scythe, Grim come to collect those whose time has come and escorts them to the 'other side', in other words, Grim's occupation is primary as a psychopomp: In Schlubs, Grim comments upon how he used to charge two coins for ferrying souls across the River Styx. But Grim also has power over life and death, as he is able to extend someone's life, (as seen in Jeffy's Web,) and can be challenged to stop someone from dying, (as seen in Meet the Reaper). On the darker side, and more biblical of the role of the Grim Reaper, Grim, as Death, and armed with the scythe, is meant to "carve a swath of despair and destruction through the world of men, to blacken the skies and redden the seas, leaving nothing behind but entropy and uncomfortable silence...".
While the position of the Grim Reaper is a privlidged one, Grim is not immune from punishment for misuse of his power, as seen in Home of the Ancients when he had used his powers to pull the moon out of orbit and used it as a bowling ball for Billy and Mandy.
In the episode The Halls of Time Grim is seen has having a very special sand timer, larger that regular humans, and full of Black Sand. In the episode Duck!, Grim explains to Billy that, as the Grim Reaper, Grim cannot have good dreams, if ever Grim should have good dreams, then a vortex would open in the back of his skull, giving all manner of unsavoury 'buggaboo's access to the human world. In the episode Scythe 2.0, Grim can go to F, a humanoid, Q-like character in the Underworld who is responsible for repairing the scythe. In The Love that Dare Not Speak Its Name, Grim's profession is touched upon as less about reaping a person whose time has come, as Grim is shown explaining to Billy that "the first rule to a successful reaping is selection".
Several conflicting accounts and a number of clues have been given as to how Grim first came to be The Grim Reaper:
- Billy and the Bully: In this episode, Grim's mother is seen in silhouette, in the same foreboding robes as Grim, hinting that the position of the Grim Reaper is hereditary.
- Lil' Porkchop: In this episode, when Grim shows Mandy a picture of his old pet skeleton fish, called "Chugney", the picture also shows Grim as a preteen in his traditional foreboding black robes, supporting the back story that Grim's position as the Grim Reaper is hereditary.
- A Grim Prophecy: In this episode, Grim is shown as having been forced into the role of the Grim Reaper by both his parents, further supporting that Grim's position as the Grim Reaper is hereditary.
- Dad Day Afternoon: In this episode in season 6, Grim is shown as becoming the Grim Reaper after coming across the scythe randomly, unbeknownst to his father, whom Grim lead to believe that he had become a Country Western Rocker.
- King Tooten Pooten: In this episode in season 7, Grim muses over his time as an intern for Osiris, God of the Egyptian Afterlife before he became the Grim Reaper.
- Wrath of the Spider Queen: In this story, Grim was elected to the role of the Grim Reaper by his classmates after his display of supernatural power.
Other episodes don't support the above:
- Bully Boogey: In a flashback in this episode, Grim is seen in ordinary clothes as a child and not in his robes.
- The Secret Decoder Ring: In a flashback in this episode, Grim is seen in ordinary clothes as a child and not in his robes.
As a supernatural creature of the Underworld, Grim naturally has supernatural powers of his own, such as being able to grow in size and warp his form and the ability to possess the living, (as seen in Get Out of My Head). As an 'undead, talking magical skeleton', Grim is a complete animated skeleton of bones that is able to function both as a complete skeleton or independently as individual bones. Grim has also been seen creating flames whenever his tempers flares, even his eyes will shoot out flames when he gets angry or determined. It can also be seen that Grim has telekinesis. He used this when he flew the Chupricabra tape into his hand out of the VCR.
Beyond this, Grim has demonstrated the use of spells in earlier episodes; consulting with Underworld editions of books and manuals of magic, (such as in Tickle Me Mandy when Mandy went away for a day, Grim used some of Billy's toys to make a 'Mandy-Substitute' to keep Billy company). Grim owns copies of Underworld tomes such as "The Bad Book", the "Destruction Manual", "The New Jersey Book of the Dead", and "The Monster Manual - vol 1". Possibly because of his profession as the Grim Reaper, Grim has the power to extend any living thing's lifetime by adding sand to their hourglass (shown to be manufactured by Father Time) which he does to Jeff so that he can keep scaring Billy.
As the Grim Reaper, Grim is the "Master of the Forces of Life and Death" and the owner of 'The Reaper's Scythe'; an Underworld object of power, (other such objects of power include, Eris' Apple of Discord, Pandora's Box, and Horror the Ancient's 'Left Hand of Horror'). All the most prominent of Grim's powers stem from this scythe. For the most point, Grim is dependent upon the scythe in the series for his powers and is usually rendered powerless when disarmed, but has been seen shown as capable of magical feats without it.
The Reaper's Scythe has the ability to cut and slice through anything and, according to Jack O'Lantern in Billy and Mandy's Jacked Up Halloween, anything that has been cut by the scythe's blade cannot ever be repaired. The Reaper's Scythe can be used to open rifts to 'the other side' it's main purpose being to open the way for the souls of the recently deceased to pass through.
The scythe, however, is not limited to just cutting through obsticles and opening portals, as Grim has also used it to open inter-and-extra-dimentional portals and rifts in the fabric of time and space, and cast spells. The scythe's blade can be used to fire bolts of energy at targets, give off light, deflect incoming energy blasts and put up protective barriers (Which Came First?,) and the handle can be used like a Lightsaber, (Brown Evil).
In Hurter Monkey, it was shown that the Scythe is able to hold Grim to his promise to be Billy and Mandy's best friend, preventing Grim from leaving Billy's house with the intention of never coming back. In Billy Idiot, Grim admits that the only way a evil witch can overpower his scythe is if she can first turn it into a snake, and then turns it against him. In The Grim Adventures of the Kids Next Door it is shown that Grim could feel that the scythe had become fused with a bunch of children who were evil, but oddly delightfull.
Grim is also in possession of a Magical Trunk, larger on the inside than it is on the outside, Grim stores a menagerie of sinister, evil, and, more importantly, dangerous magical objects for safekeeping. A handful of episodes show the calamities that follow when Billy, having unheeded Grim's instruction not to do so, opens and takes things out of Grim's trunk.
Grim's Black Robe is also magical, aside from being able to expand along with him whenever he shapeshifts, Grim's robe has been seen as sustaining damage and then seen again intact. In Sickly Sweet, it is revealed that aside from keeping cursed objects within his trunk, Grim explained to Billy that he also keeps "terrible, cursed objects", such like magical metal gloves, or "The Mask of the Beast" in the pockets of his robe.
A running gag in the show involves various people hilariously and pathethicly stealing his scythe according to Billy and Mandy's Big Boogey Adventure:
- Jack O' Lantern
- Billy's other cousin
- General Skarr
- Principal Goodvibes
- Mrs. Claus
- The Secret Snake Club
- The Army
- Scout Troop 701
- The Sleestecks
- Abraham Lincoln
- The Mailman
- The Dinglesmidght Sisters
- Boogey Man
- A llama
- A turkey salad sandwitch (hold the mayo)