The Quarter is an object owned by Karl Kreutzfeld. It has the power to extrapolate the memories of whoever swallows the Quarter and make them solid. Karl uses it to create a 'ghost' of his son after he died from Leukimia.
The memories are given a solid form which lasts for a few days. The user can shut it off at will and the effect presumably ends automatically when the coin is passed by bowel movement. People created from the memories seem to display little or no independent personality, and at best act as the bearer remembers they would have acted.