Raised by a Metal Monster

Nobody knew where the boy came from. Or why he was partially robotic. Or why he could replicate and mimic other people's voices perfectly.

He didn't know his name, so he just told them to call him Echo. But he was trying to hide. Hide from a metal monster that escaped and called him its son and made him like it.

R. L. Stine found the boy while he was running away. He brought the distorted boy to his house and claimed that he wrote the story of the partially robotic boy. Hannah takes the boy as her new brother, but things get fishy when Slappy escapes due to Zach and Champ. Due to the action, the Mimic discovers the Goosebumps monsters and begins to act and mimic the actions of the monsters in order to find Echo and bring him home.

Oh well, Echo knew that he couldn't escape from the metal monster that forced him to be a part of its family.