The Incredible Shrinking Fifth Grader

Unreleased The Incredible Shrinking Fifth Grader was going to be the twenty-sixth book in the Goosebumps Series 2000 book series. It was never released due to R.L. Stine's contract with Scholastic expiring.

History
The title of the book was publicly revealed in a March 1998 article on the Goosebumps fan-site, The Bumps, along with other Goosebumps Series 2000 titles. Tim Jacobus completed the cover illustration in 1999, but before he could submit it, a Scholastic representative called and told him not to turn in the artwork, asserting that it would be his final Goosebumps cover. Due to legal disputes between Scholastic and Parachute Press, Scholastic opted not to renew R.L. Stine's contract, meaning the book's planned Series 2000 release had to be canceled.

In an interview from March 6, 2017, Jacobus described the book's cover and cancellation in detail. Jacobus shared the unused artwork three days later on March 9 after receiving a request from a fan. The cover depicts what would be a scene from the book, showing miniature-sized kid holding a pencil, warding off a white rat while standing atop a classroom desk.

The scene depicted on the cover, along with the plot of a shrinking fifth-grader and being inspired by the film The Incredible Shrinking Man bares a striking resemblance to the R.L. Stine book, The Adventures of Shrinkman, which was released very shortly after the cancellation of Series 2000. On November 14, 2017, R.L. Stine confirmed on Twitter that the plot for The Adventures of Shrinkman had in fact evolved from The Incredible Shrinking Fifth Grader.

In November 2021, an art book titled The Art of Goosebumps was released that revealed early concept art of The Incredible Shrinking Fifth Grader that featured a rabbit instead of a rat. It also revealed that a book titled When the Snake Bites was planned to follow this book, though a cover was never illustrated for it. The Art of Goosebumps also features concept art from The Adventures of Shrinkman.

Trivia

 * A Goosebumps book featuring a shrinking protagonist was eventually released in 2011 as the Goosebumps Hall of Horrors book, Night of the Giant Everything. Though, whether it borrows elements from The Incredible Shrinking Fifth Grader is unknown.
 * The title being revealed in March 1998 means it evidently predates any mention of Ghost in the Mirror.