Despite its apparent usefulness, the Ethicator was a failure, evidenced when the duplicate began writing embarassing love letters to Susie Derkins. Calvin had unintentionally integrated a Moral Compromise Spectral Release Phantasmatron into the Ethicator, meaning that if a "good" duplicate had an evil thought, it would vanish to prevent defeating his purpose. Presumably, it worked the opposite way for a "bad" duplicate.