Professor E. Gadd's Research Journal

Professor E. Gadd's Research Journal is an anecdote published on the official website for the Nintendo 3DS version of Luigi's Mansion. It is a journal in which Professor E. Gadd relates the accidental discovery of a green slimy, "Goo," responsible for the creation of Gooigi. The only entry in the journal so far is XXX-001 An Accidental Discovery.

Summary
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.