Art by Nigel Kitching
Amnesia spray is a chemical agent created by the mysterious Mystery Man, man of mysterious mystery. By spraying on an enemy's face, the victim immediately loses all of their memories and becomes one of the Mystery Slaves.
When Chuck D. Head (as Decap-Man) was somehow captured by the Mystery Man, the supervillain challenged the hero to guess his identity. If Chuck failed, he would be hit by the spray. Inevitably, Chuck was unable to win the challenge and was sprayed. However, it all turned out to be a dream, with the sensation of being sprayed actually being from Igor throwing a bucket of water on his face.