Was Once a Man/Playing With

Basic Trope: A monster who used to be human.
 * Played Straight: The Evil Bob-Thing used to be Bob.
 * Exaggerated: All monsters were once humans.
 * Downplayed: Bob becoming Alice is treated as this.
 * Justified: This is the only way new monsters can be created.
 * Inverted: Bob is a human who used to be a monster.
 * Subverted: The Bob-Thing was always a monster.
 * Double Subverted: The Bob-Thing was lying.
 * Parodied: Bob gets turned into a cute bunny rabbit. Or, a friendly monster character mentions in passing that it used to be human, but didn't much like it.
 * The monster was once named "A. Man", but had it legally changed.
 * The Bob-Thing was once a man, despite being a woman.
 * Zig Zagged: Bob keeps repeatedly changing between his human form and his monster form.
 * Averted: Bob stays human.
 * Enforced: The writers wanted to give a psychological aspect to the horror by having it being once a man.
 * Lampshaded: "That thing... it wasn't always like this."
 * Invoked: Bob does everything he needs to do to become a Bob-Thing.
 * Defied: Knowing that there is a very real chance that he may turn into a monster, Bob seeks to prevent it.
 * Discussed: "Oh my god... now we know what happened to Bob."
 * Conversed: "In stories like this, the most inhuman monsters were all once humans."
 * Played for Laughs: ...
 * Played for Drama: Due to the nature of this trope, almost every example will already be played as this.