Neuralyzer

A neuralyzer is a gizmo from Men in Black that erases memories. It is used by the PPC to make canon characters forget Suefics and extra-canonical anything. It is also used by the Department of Internal Operations to make Agents forget the DIO's existance.

Originally, use of the neuralyzer was not needed, as the canon would tend to reassert itself and reset things to their proper state. It still does this, to a degree, but in recent years the various Word-Worlds have become so badly battered and stretched by the influx of Sues and other canon-damaging influences that with a very few exceptions, canon characters have come to require neuralyzation for things to fall back into their proper alignment.

See also Mass Neuralyzer.