Professor Elvin Gadd

Professor Elvin Gadd, also known as Professor E. Gadd (often Dr. E. Gadd; Japanese: オヤ・マー博士 Doctor Oya Mā), is the scientist first appearing in Luigi's Mansion and founder of Gadd Science, Incorporated. He always speaks in ambiguous gibberish (supplied by Kazumi Totaka, who took inspiration from Animal Crossing's "Animalese" when inventing the voice ). His name comes from the minced oath "egad!", something that one says in amazement or shock.

Background
He used to live on the foothills of the Thwomp Volcano, as depicted in the game Mario & Luigi: Partners in Time.

The Mario Bros. go back in time and end up saving his lab from burning down when fire blocks erupted from the Thwomp Volcano. He then helps the Mario Bros. by inventing the Hydrogush 4000. Although he doesn't directly invent the Hydrogush 4000, his older self does in a complex way: Young E. Gadd starts to get an idea after a totally unrelated event happened during the present time, which transfers to his future self, causing the present-day, elderly professor to send water from the Hydrogush 4000 via Time Hole and calm the erupting Thwomp Volcano. After all this excitement, the twenty-year-old E. Gadd moves to Boo Woods.

Luigi's Mansion
Many decades later, in Luigi's Mansion, Luigi enters the mansion and is saved from ghosts by a strange old man wielding a vacuum cleaner. Professor E. Gadd reveals he lives in a house near the mansion, where he researches his favorite subject: ghosts. Luigi explains his brother Mario is missing within the house, and the professor decides to help Luigi by giving him two of his inventions, the Poltergust 3000 and the Game Boy Horror. The professor continues to help Luigi throughout the game, giving him help and tips.

Luigi's Mansion: Dark Moon
After a few years of absence, Professor E. Gadd appears in the game Luigi's Mansion: Dark Moon. In the game, E. Gadd takes up residence in Evershade Valley after learning that the ghosts there are friendly. Eager to examine ghosts without fear of being attacked by them, he sets up a laboratory in the Gloomy Manor and a Bunker close by the mansion. There, he begins researching the ghosts of the five mansions that populate the valley, and sends his five Toad assistants to the other four mansions in the valley to examine the ghosts there. At first, the resident ghosts welcome him and assist him in his lab, but when King Boo arrives and destroys the ghost-pacifying Dark Moon that hangs over Evershade Valley, the ghosts start running amok and destroy E. Gadd's equipment. He flees to his nearby Bunker and enlists the help of Luigi &mdash; who has now taken up residence in his new Grade D mansion from the previous game &mdash; to help rebuild the Dark Moon and calm the ghosts once more. E. Gadd was later revealed to have been unintentionally and indirectly responsible for King Boo's return, as he had sold his portrait in a garage sale, thus ensuring his escape.

In this game, E. Gadd has made an upgrade of his Poltergust 3000 from the last game: the Poltergust 5000. This new Poltergust uses a Strobulb to stun ghosts, rather than the flashlight used with the Poltergust 3000. Professor E. Gadd also introduces three new inventions: the Pixelator, a machine that turns Luigi into pixels and transports him to and from the different mansions, the Dual Scream, a device that resembles a Nintendo DS and is capable of communication, and the Dark-Light Device, which allows Luigi to see invisible objects.