Professor E. Gadd's Research Journal

Professor E. Gadd's Research Journal is a series of stories written in journal format on the official website for the Nintendo 3DS version of Luigi's Mansion. In it, Professor E. Gadd relates the accidental discovery of a green slimy, "Goo," responsible for the creation of Gooigi.

XXX-001 An Accidental Discovery
E. Gadd begins by making a short introduction on a "strange liquid energy" collected from ghosts he had befriended. He posits that said energy is "the key to many, many new inventions," but admits that he initially struggled to uncover its uses. His failed experiments with the energy included poking it with iron, pouring it on rubber, and even absent-mindedly dipping a donut into it.

The professor recounts that later during his research, he was startled by a Hider ghost that had escaped from its confinement, causing him to spill the coffee he was drinking into a vial containing ghost energy. He claims that the coffee, described as a "Lunoman Greenie blend from Evershade Valley," quickly reacted with the energy inside the vial, leading to the creation of a green viscous substance. E. Gadd recognized the substance as a new chemical element and called it "Goo," which he then assigned the "00" entry in the.

XXX-002 Characteristics of "Goo"
E. Gadd writes that he wishes to discover the real-life uses of "Goo", and decides to perform various expirements on it. He first tested fire on the Goo. The substance was melted, revealing a weakness to fire. The professor followed up by spraying water on the Goo, which yielded the same result. However, E. Gadd notes that the bits of Goo which did not touch the water had moved away from the hazard.

The professor also tells that he has discovered other unusual properties of Goo. He reveals that Goo will push back when touched, as well as react to sounds such as music. E. Gadd concludes that Goo is able to react to outside stimulation, and writes that he believes there is a greater purpose for this new element.

XXX-003 The Birth of Gooigi
E. Gadd writes that he could teach Goo to collect ghosts with his invention, the Poltergust 3000. He first created a mold that he could pour Goo into a humanoid form. When he removed the mold, Goo was in a human shape, but returned to its original form moments later. The professor then used the Pixelator that contains Luigi’s biological data and converted it into an electrical signal. He then was able to input the signal into the Goo. The result was that the Goo has shape-shifted into a green copy of Luigi.

E. Gadd then showed the Goo some footage of Luigi catching ghosts. The Goo began to imitate Luigi’s movements, and even grew a perfectly functional replication of the Poltergust out of its body. E. Gadd decides to call it Gooigi and is determined to find the perfect place to test "his" abilities.

XXX-004 That Nostalgic Mansion
E. Gadd decides to begin teaching Gooigi how to catch ghosts, but wonders where to do it. E. Gadd also states that he needs ghost energy from beyond Evershade Valley to give Gooigi capabilities beyond that of a normal person. He then concludes that sending Gooigi elsewhere is a good idea, since Gooigi could learn more from fighting ghosts and could collect them at the same time.

After gulping down some Lunoman Greenie coffee blend, E. Gadd thought of the perfect answer: send Gooigi to the mansion where he first met Luigi. But the mansion had vanished a long time ago, so it was impossible to walk Gooigi there. However, E. Gadd was able to modify the Pixelator to connect it to the past. Afterwards, he contacted E. Gadd and Luigi from the past, asking them for help, and sent Gooigi to them.

After some time, E. Gadd contacted Gooigi to check up and found that Gooigi collected a lot of ghosts and also succeeded at every challenge he had faced. Afterwards, E. Gadd then began to think of the possible interactions between ghost energy and Goo.