Porter is slim yet stocky build ghost with slime green skin and dark green hair with long bangs swept to the left. His limbs are fading away and transparent, and has dark-green eyebrows that match his hair. Porter has intense blue eyes with two green sclera and black pupils.
He wears paint-artist inspired clothing that are colorful and look like they have been painted; he wears a black shirt and a black brick-pattern shorts with paint-like stains all over his clothes. He wears a shackle on his left wrist and chains wraps around his waist, with two chains dangling on his sides. He wears blue shoes and has two painter spray cans of "ghost paint" attached to the chain suspenders on his shirt.
Free-spirited, rebellious, and honest, Porter has been labeled several times as part of the "bad boy" type due to spreading his graffiti art everywhere around the school and has accumulated more "Detention Chains" than anyone else in school. Porter's nickname "Paintergeist" comes from his love of art and loves painting on everything. Whenever inspiration strikes, he wastes no time in finding the nearest canvas, usually a wall, and painting an image in ghost paint. Despite Porter's art constantly lands him in trouble with Principal Revenant, he always remains upbeat, friendly, and cheerful, always looking for his next masterpiece. However, Porter's playful and laid-back behavior makes it hard for other to take him seriously unless he outwardly shows it. Porter proves to be crafty and observant, such as getting past the Hall Moanitors long enough to paint his artworks. Porter is also is the only student at Haunted High to notice the increase of detention chains that Principal Revenant been giving out unfairly. He also was able to steal the key Principal Revenant uses to transfer her chains to the students and plays along with her deal to betraying his friends in order to see how the key works and free them later.
Though sometimes coming off rude and often considers to be a troublemaker, he has a soft side and greatly cares about his friends. Porter is very considerate whenever he's creating artworks, as he hates ruining other people's property, so he only paints using "ghost paint", a type of paint that fades away after a while, and only permanently paint something if he owns it. In In her Kiyomi Haunterly's dairy, Porter spray painted a touching haiku for her when he notices she been feeling down lately. In the Haunted, Porter offers to take on all the Detention Chains of the other students as Spectra Vondergeist and her friends work to stop Principal Revenant's plot to invade the Monster and pass off her punishment chains to innocent students.
Porter is a ghost and therefore hold abilities of a regular ghost.
- Permeation: Porter can pass through solid matter.
- Floating: Porter can float.
- Artist: Porter is a skilled artist, particularly in using spray cans and paint, but is also good as drawing pictures with pen or pencil. Porter demonstrates the ability to telekinetically control his spray cans and paint cans by waving his hands and arms around.
Porter is the son of the Poltergeist, which may or may not be his father.
Porter attends Haunted High, and is good friends with Vandala Doubloons, Kiyomi Haunterly, and River Styxx. In her dairy, it mentions that Porter hangs out with Kiyomi sometimes, even before she became popular, and openly compliments her, which she appreciates and might have slight attraction to him as a result.
Porter has an mutual interest in Spectra Vondergeist. They met in the Monster High movie Haunted when Porter was getting chase by the Hall Moanitors and nearly crashing into her, implying that it was love at first sight for Porter and Spectra. Throughout the film, Porter shows he cares very deeply for Spectra by helping her around Haunted High after she got trapped in he school and separated from her friends. Although Porter's antics and jokes occasionally annoyed Spectra, he makes her laugh and Spectra assist Porter in trying to figure out Principal Revenant's secret plans. Porter is very open in his showing his affections for Spectra, as Porter called them a "duo" and on many occasions complimented Spectra, whether he meant to or not, such as saying she was smart and touching her hand when comforting her. Porter even went out of his way to fix up a old writing desk to give to Spectra, causing Spectra to hugged Porter. When Spectra was going to confront Principal Revenant, Porter said "No! I could lose you." and save her from getting capture by following Spectra to the office, showing how much he cares for her safely
In return, Spectra welcomes Porter's compliments and two quickly become close. Spectra expressed her worries about Porter when he stayed back at Haunted High when he's covers in detentions chains, wishing he could come with her and kissed him on the cheek for all his help. At the end of film, Porter and Spectra begins a somewhat long-distance relationship as she returns to Monster High and he stays at Haunted High.
- January 22, 2014: Mattel requests the trademark for Porter "Paintergeist" Geiss.
- July 26, 2014: Preview photos of Porter "Paintergeist" Geiss reach the internet seconds after the reveals at San Diego Comic-Con International.
- Spring 2015: Porter "Paintergeist" Geiss makes his 3D cartoon debut in "Haunted".
- Porter's OBEY art is a reference to the 1988 scifi movie They Live and the 1989 Andre the Giant Has a Posse street art campaign it inspired.