

McGucket also became immune to any further memory wipes, as seen when Blind Ivan attempted to use it on McGucket. The device's inventor, Fiddleford "Old Man" McGucket, used it on himself more than anyone else he slowly went insane, lost all of his memory, and was changed into his current appearance before 1982 as a result. The severity of the effects increases with the amount of use, ranging from minor brain damage to total memory loss and eventual insanity. Repeated use of the device results in drastic side effects. As seen in " Society of the Blind Eye" and " Weirdmageddon 3: Take Back The Falls," it is possible to reverse the effects by presenting the forgotten memories, gradually allowing the person to retrieve the piece of memory that was erased.If it was used on Ford, the metal plate in his head would stop any effects of it.Several members of the society use the gun on themselves, including Bud Gleeful and Blind Ivan.Memories erased by the gun are stored in The Hall of the Forgotten, and the memories are stored in the form of videos.The Memory gun destroying Stan's mind Use Afterwards, it was stepped on and destroyed by Mabel during the twins' birthday party so that she would never forget Gravity Falls and her friends. In " Weirdmageddon 3: Take Back The Falls," the gun was used by Ford to erase Bill when he was tricked into entering Stan's mind. After Dipper discovered fragments of Ford's memories of Bill Cipher, he attempted to use the gun in a frantic attempt to eliminate Bill from Ford's mind, but it is revealed that Ford is immune to the gun's effects due to a metal plate in his head, so the ray bounces off his forehead and destroys Project Mentem. In " The Last Mabelcorn," the gun is kept in Ford's hidden office. The Memory gun resting in Ford's Private Study When he sees the device, Ford says "I don't know how you got a hold of one of these," which seems to imply that there are more similar devices, and that he had encountered them before. He gave it to Ford so he can use it to erase the memories of the government agents so that they forget about Stan and the twins before they could discover the universe portal, which he accomplishes by converting the beam into a sound frequency and broadcasting it around the Mystery Shack.

In " A Tale of Two Stans," it is revealed that Dipper has kept the gun. Later, the society members try to use it on Dipper and his friends when they were discovered, only to fail and get their own memories erased instead. When Mabel got her hands on it, she wanted to use it to forget about her past relationships, but ultimately decided not to along with Wendy, who was tempted to erase her memory of an annoying rap song. In " Society of the Blind Eye," it is used on Lazy Susan so she would forget about seeing the gnomes. The members of the Blind Eye Society decided to use the device in order to help the citizens of Gravity Falls forget "all the things that go bump in the night." He eventually began using it so frequently he lost much of his memory, and ultimately became senile. The memory erasing gun was created by Fiddleford McGucket, originally intended for the purpose of allowing him to forget certain memories, due to the guilt of helping Ford Pines build the Universe portal.
