|I am not a ghost, or a spirit or a phantom. I am invisible.|
|—Invisi Billy in Invisi Billy's New Scaremester diary|
Invisi Billy is a 2012-introduced and all-around character. He is an invisible boy and a student at Monster High. Outside of classes, Invisi Billy can regularly be found in the vampitheater to help Mr. Where with the next production. Like his father, Invisi Billy loves creating and has a knack for special effects, even if all it sometimes is is him walking around invisible while holding an item. He also loves to use his power for the occasional prank, especially if he can make someone feel better with it. He dates Scarah Screams, who can always detect his presence by checking the minds around her. Invisi Billy takes on the role of chairman of the Disappearing Club after school, which is a small but supportive group of friends who appreciate the art of disappearing.
Invisi Billy is voiced in English by Evan Smith.
Invisi Billy is a nice guy who minds his own business, and is definitely caring and willing to help whoever needs help, through his invisibility powers. He is full of whit and smart and definitely knows how to apply his abilities in strategy. He does this a lot to live his passion, special effects. He adores working backstage to theaters and musicals, which comes in handy since he is a quiet soul, and with his invisibility he is able to create the most fantastic of effects.
However, he is also a guy who loves his mischief, using his powers for pranking, regularly. He's a total prankster and his brains help, and when he can make someone feel better with his jokes he's a happy camper. Despite this, he isn't abusive of his powers and knows the limits of good and bad, and usually only sticks to good and mischief. He refuses to use his powers in ways people aren't comfortable with and respects people's privacies, even if he struggles to keep visible most of the time.
He loves life and enjoys living it freely, but never at the expense of others. He still enjoys his jokes and being silly but wouldn't do anything that would affect someone greatly. He is sometimes called by his nickname Billy.
Billy has an icy blue skin tone bordering on white, grey eyes, and his hair is a dark shade of blue when he is visible. This gives him a bad-boy type look. When he is invisible he is completely transparent with little sign of him being there.
Invisi Billy is the son of the Invisible Man. If the "New Ghoul Materializes Just in Time for Día de Los Muertos" article is to be believed, he has siblings.
Invisi Billy used to have a pet dog, but he had to give him away because he couldn't walk him without animal control thinking the dog was a stray. Since then, Invisi Billy has acquired a box, which may or may not contain a cat which on his box is called "a quantum cat".
Invisi Billy is popular with the ladies, who've started calling him "Drop Dead Dreamy"! This is because when he is not in invisible form, his true appearance is obviously seen, which most female monsters find his appearance attractive. His own dream-girl is Scarah Screams, whom he hooked up with in "Scarah-Voyant". They are again announced as a couple according to "13 Wishes" and his 'New Scaremester' diary.
- March 14, 2012: Invisi Billy appears in the Spanish release of "Scare-born Infection".
- April 01, 2012: Mattel introduces Invisi Billy on Facebook and Tumblr.
- April 01, 2012: Invisi Billy's profile art is revealed.
- April 16, 2012: Mattel requests the trademark for Invisi Billy.
- April 20, 2012: Invisi Billy makes his 2D cartoon debut in "Unearthed Day".
- September 26, 2013: Invisi Billy makes his 3D cartoon debut in "13 Wishes".
- December 03, 2013: Invisi Billy's updated profile is published in the 5th issue of the USA Monster High magazine. The profile includes redone profile art.
- Early 2014: Invisi Billy's debut doll is released as part of the New Scaremester series.
- May 29, 2014: Invisi Billy's profile is published on the Monster High website and promptly removed.
- June 05, 2014: Invisi Billy's profile is re-published on the Monster High website.
- Late June, 2014: Invisi Billy's debut doll is released as part of the New Scaremester series.
- Invisi Billy was officially introduced to the fanbase as an April Fools' Day joke in 2012. Both the Monster High Facebook account and the Gory Gazette were updated with pictures and articles on a new student at Monster High. The pictures contained empty boxes, with the taunting quote "How do you know I am not in the box?", while the profile revealed that Invisi Billy was a prankster. Later on April Fool's Day, Mattel announced the joke, explaining that Invisi Billy was real but that he wouldn't come out any time soon.
- Two weeks prior to Invisi Billy's reveal, a number of webisodes had their respective versions uploaded on the Mexican and Brazilian Monster High websites. Among them was "Scare-born Infection", which features Invisi Billy prominently, so a part of the fandom knew he was going to be real.
- Invisi Billy's pet, a box which may or may not contain a pet, is a reference to Schrödinger's cat - a famous thought experiment on the concept of quantum mechanics.