I.M. Spooky writes Spineticklers which is a spin-off of Goosebumps by R.L Stine. It is unknown whether it's a pen name, and if it is, what the real name of the writer is, and regardless of whether it's his real name, it is unknown what the I and the M stand for. Even on the "about the author" section it just says that the publishers don't know much about I.M. Spooky except that he's a man and he's writing the next book. As such, when Greg and several of his classmates tried to write book reports about him, they failed. Susan thinks it is just a name for a group of authors who write the books. Greg supposes that if "I.M. Spooky" is his real name, he'd have to write scary books, and he thinks that if it is a pen name, he mustn't tell Rowley as Rowley wrote a letter to a "Mr Spooky".
- Diary of a Wimpy Kid: Double Down (First and only appearance, mentioned)