William "Billy" is the deuteragonist of the show. He is a dim-witted, happy-go-lucky boy living in Endsville. He is best friends with the Grim Reaper and Mandy, who treats him more like a servant than a friend, never being one to pass the opportunity to exploit the stupid. He was born with an extremely low IQ of -5, having been outperformed by a shovel and 2 candy bracelets on an IQ test. Good-natured and incredibly dopey, Billy's curiosity tends to get him into trouble he can't get out of by himself. Billy enjoys the company of Mandy and Grim and would do just about anything for them.
Billy and Mandy met as babies when he came over to her house, repeatedly ringing her doorbell to annoy her enough to answer. When she did, the first thing she said to him was, "Are you some kinda idiot?". When he pointed out that she had no nose, he proceeded to shove an ice cream cone into her face, apparently creating a makeshift nose for her. Angered, Mandy punched Billy in the face, calling him a creep, and slammed the door in his face. Billy simply laughed and said, "She digs me". According to Harold, that day was the start of Billy and Mandy's friendship.
Years later, while Billy and Mandy were celebrating the tenth birthday of his pet hamster, Mr. Snuggles, the Grim Reaper appeared to claim the old hamster's soul. However, Mandy refused to give the Reaper the hamster and offered to play a game for its soul instead. If the Reaper wins, he would get the hamster's soul. Grim, assured of his victory, sweetened the deal on their behalf by promising that if they win, he would be their best friend "forever and ever." Grim took Billy and Mandy to play, where they competed in Grim's favorite game—limbo. Mandy cheated, and Grim was doomed to be the "best friend" of the two kids for all eternity.
Due to Billy's idiotic, foolish desires, which he orders Grim to bring about, he is often the cause of Grim and Mandy's mishaps. Billy, despite being a complete moron, sometimes has random bursts of cleverness and cunning, especially when he wishes to attain his said foolish desires. Although good-natured and happy-go-lucky, he has occasional fits of stubbornness, violence, anger, and rage, which shows insanity that even Mandy seems to fear. While Billy is the most innocent character of the three, he ends up causing the most problems due to his irrational and often impulsive choice of actions, usually by deliberately doing what the others expressly told him not to do. Billy is terrified of clowns to the point of having recurring nightmares about them, although eventually, due to an encounter with his inner frat boy, his fear is transformed into a psychotic loathing and hatred for them, as shown in Attack of the Clowns. He is also scared of the mailman and spiders, which is quite unfortunate because he is Jeff's father (Billy hatched his egg), and Jeff is a huge spider.
His stupidity has seemingly given him the power to be extremely oblivious to pain as in many episodes he is shown to be having his own flesh rip apart like his nose exploding or bones jutting out from his body. He can be seen immortal in this sense as he has always been able to get out of seemingly lethal encounters, with or without Grim or Mandy like his encounter with the Kraken.
He is also shown to hate rules which an entire episode is dedicated to this hate in which he learned his lesson when he got eaten by an alligator and broke his dad's motorcycle.
Billy has an extremely large pink nose inherited from his father, Harold and orange-ginger hair from his mother, Gladys. He wears a white t-shirt with horizontal blue stripe, dark blue jeans and covers his ginger hair with a dark red hat. He also wears white and red sneakers.
He becomes a scientist for Underfist later on. By then, he starts wearing safety goggles, a white lab coat, purple gloves, and black boots.
Powers and Abilities
- Heightened pain tolerance: In many episodes and because of the fact that he is in an animated cartoon, he is shown to have his flesh ripped, body parts cut off, burned, eaten, and many other seemingly lethal encounters but always ends up surviving what would normally kill off other characters. This may be due to his stupidity to be so heightened that he is oblivious to pain and danger that he is indifferent to it as he is to life itself.
- Heightened Confidence: He is shown to have no shame or fear in certain times of danger which can prove useful to him being oblivious to the danger which goes with his pain tolerance that makes him the stunt monkey and meat shield of the trio.
- Nose Mucus Adhesive: Billy can make use of his nose mucus to make things stick together like when he used his snot to fix the dismembered boat in the movie.
- Master Distract Artist: He is shown to be effective in distracting and buying time for people like in the Halloween movie where he is able to distract Jack by mooning him long enough for Mandy to set up an abundance of prank traps.
- Taunting: Going with his distracting capabilities, he is has the ability to be so annoying and taunting that he can send anyone into a fury to go after him like in the anger mismanagement episode.
- Nose Balloon Lift: It is shown that his noes can be used as an inflatable hot air balloon and can be held on by the nose hair to fly.
- Befriender: Billy has the ability to be attached and befriend to unlikely beings to have mutual likings with each other. Whether it be inanimate objects like rocks, to underworld mutants like the kraken or the chacabra, or even Sperg temporarily in some episodes. This is limited to unfortunately to anything he does not fear which includes spiders, the mailman, and clowns in which he will act hostile or scared to.
- Unlikely Translator: Billy at times is shown to speak of things only he can say like when he did a special call to signal the kraken to help them win a race. He could also understand and cunningly make Fred Fredburger's seemingly meaningless phrase about eating nachos into a moral of the story about their capabilities in the movie.
- Super Yogurt Hero: He has the ability to turn into a muscular green superhero that can fly, have super strength, and shoot strawberry yogurt from his armpits.
- Werewolf: Although temporary, Billy turned into a werewolf by the zombie martians in one episode.
- Uniquely Stupid Brain/ Living without a brain: Billy's brain is so uniquely stupid that it had the power to destroy a brain washing machine the martians had. However, he may not even have a brain also stated in some episodes which shows he is able to function (although extremely low intelligence) normally without one.
Relationships with other Characters
After having lost a game of limbo to Billy and Mandy, Grim was forced to become the two's best friend forever. If Grim doesn't honor his commitment to be Billy and Mandy's best friend forever he'll go to under world jail. Billy is seemingly aware that Grim doesn't like him, most likely because he tells Billy that at every opportunity. However, he still treats Grim like a valuable and loyal good friend, even if he never listens to him. Nevertheless, Grim has shown that he seems to like and care for Billy, and would rather be with him than Mandy since she always orders him about and abuses him to her own selfish ends.
Despite being best friends, Mandy treats him more like a servant than a best friend, never being one to pass up an opportunity take advantage of his stupidity. Billy either seems to not notice this or enjoys it considering the only time he ever shouted at Mandy about her treatment of him was when she said, "Thank you".
It's possible that Billy may secretly have romantic feelings (whether or not he actually realizes it), because he's suggested getting married to Mandy at least three times--an example being when he seemed rather eager to marry Mandy when Judge Roy Spleen initially mistook the trial in "Keeper of the Reaper" for a wedding ceremony--and he has kissed Mandy (or even licked her face) a few times throughout the series.
Billy has protected Mandy a few times, an early example being in Little Rock of Horrors, when he tried protecting Mandy from getting her brain taking from the alien-meteor. Also, despite generally treating Billy with contempt and more like a servant than a friend, Mandy seems to genuinely care about Billy, as she's protected him many times throughout the series and is the one person she actively hangs out with outside of her family. However, it's unknown if Mandy's feelings are strictly platonic or possibly romantic, Grim sometimes teases them about it.
Billy gets along with Irwin more than anyone else. The two boys’ both have much in common, they both enjoy activities which are normally nerdy. But they are also extremely different; although Irwin has his moments of stupidity, he is also very smart and is considered a 'math nerd', 'socially inept', and 'the computer illiterate' according to Mindy.
Jeff believes that Billy is his father, which is not the best thing to be since Billy's extremely arachnophobic (meaning "scared of spiders"). Billy found Jeff's egg in Grim's trunk and since Jeff saw Billy first when he hatched from his egg, he imprinted on Billy as his parent. Since then Jeff has done everything possible to win his "dad"'s love. However, no matter how good a arachnid Jeff is, one who anyone else would be proud to call "son", spider or no spider, all Billy can see is a disgusting monster, which he beats at every possible opportunity.
Billy's adorable pink cat. Billy loves Milkshakes.
Billy's elderly 10 year old hamster. Mr. Snuggles's cage is kept in Billy's room. It was through Mr. Snuggles that Grim became Billy and Mandy's best friend forever.
In FusionFall, During the war, Billy adopted a Fusion Spawn named Runty, which later turns out to be his imaginary friend. Most of Billy's missions are rather pointless, but sometimes lead to more important tasks: Once Billy had the player retrieve Irwin's stuff, so that he may "watch it". Other times he had the player collect food and cage lining for Runty, in doing so revealing Fusion Mandy's lair in the Sand Castle. In his own self interest, Billy sent the player out to remove the Re:Fuse posters found in Habitat Homes after being paid 20 bucks to do so by the leader of the Beautification Organization, Fusion Father. Little did he know that in doing so, he caused the local Fusion monsters to return to their normal destructive selves. Due to his fear of clowns and nightmares he'd been having, Billy has the hero go south to City Point, in order to defeat the Destroy us alls. He then has you collect their noses, but Billy thinks the noses are scary, so the hero gives the noses to Bloo. Billy also tricked the player and stole his/her power of destiny, which allowed him/her to activate totems, just because he thought it was cool. Soon following Billy's attempt was Hex, who was unaware that Billy already stole the player's power. However, Mandy gives the player the Pillow of Common Sense, a strange pillow that actually took back the player's ability from Billy by smacking him with it and Mandy returns the player's powers to him/her (saying that she could have kept the powers herself but decided she already had common sense). In the last attack on a Fusion Control Center, Demongo planned to have Eduardo join the hero to provide an assault of Imaginary Energy. Billy showed up instead, thinking that the Control Center was the site of a party. He later showed up in Fusion Kevin's base under the same premise. This time however, he was able to make himself useful by overloading a force field made from imaginary energy stolen from Foster's Home, allowing the player to defeat Fusion Kevin which proves Billy is not that dumb.
- Billy is one of the many characters in FusionFall.
- He also has questionable schizophrenia, indicated in Bearded Billy when he overhears his father in the bathroom and tells his mother, "the bathroom is talking to me again," and asks her for his "vitamins".
- In The Crawling Niceness, it is revealed that he is afraid of spiders and also Jeff the Spider.
- Billy may have been responsible for Irwin's crush on Mandy; in the episode "Get Out of My Head!", he flirts with Irwin while in Mandy's mind, causing Irwin's emotional state to switch from frightened of Mandy to smitten by the remarks that Billy (in Mandy's mind) makes. This could be why Irwin has a crush on Mandy, as it had not been established until then.
- An alien in the Ben 10 series is based on Billy. The alien is orange, scaly and bloated with a large orange and pink nose, pointed ears and bad teeth. It is voiced by Richard Steven Horvitz and wears a blue and white striped shirt, and a red hat. It's species is named the Maxatomar (named after Maxwell Atoms).
- His scientist uniform in Underfist: Halloween Bash is an allusion to Dexter from the TV series, Dexter's Laboratory.
- In "Attack of the Clowns", It is revealed that he is afraid of clowns.
- Billy's intelligence can also affect reality (similar to Mandy's smile) in "Billy Gets an "A"".
- Billy's nose is removable, on one occasion even growing back after coming off.
- Also similar to Mandy, who is mistaken for a boy on more than one occasion, Billy has been mistaken for a little girl.
- It was confirmed in The Nerve that Billy had a brain, but as little as an ant.
- In Billy and Mandy's Big Boogey Adventure, it is revealed that he had three fears: spiders, clowns and the mailman. He also has a fear of the Spider-Clown Mailman.
- In an episode of Invader Zim, the title character's voice sounds reminiscent of Billy's whilst making fun of Dib. This may have been intentional, as both Zim and Billy are voiced by Richard Steven Horvitz.
- He is also allergic to blades.
- Grim & Evil
- The Grim Adventures of Billy & Mandy
- Underfist: Halloween Bash