So far, it’s been a secret, but you asked so nicely we’ll let everyone know :3
The story with extra smol Jacob is found in Brothers Found, so this tiny little guy is used to standing at a full 6′5″ tall normally! He’s really not prepared for what happens – and he doesn’t even shrink to just over an inch at the start. It begins with him ending up ‘sprite-sized,’ as Bowman so eloquently puts it.
Jacob hesitated before taking that last step and leaning on SEND; up until now, he’d merely had a view of trees and birds and squirrels at his new (hopefully not permanent) size. Calling Dean meant he’d be asking someone over six feet tall to come to his aid. With Jacob standing just over four inches, that would a huge shock.
But, he had to stop and remind himself, Dean was probably the best person to trust with this situation. Dean’s younger brother, Sam, was this size, after all. Not from the same thing, as he understood it (thankfully, since they had never found any leads on getting Sam back to his natural size), but still. Dean knew how to deal with smaller people better than anyone else. The guy would probably give Jacob endless shit about it (especially since Jacob had finally passed him in height), but if anyone in the world could help, it was Dean and Sam Winchester.
“Well? Prove that it works!” Bowman said, impatient as he stared at the device. Even when he’d seen Jacob using the phone, he never had a great angle on the object in action. He was convinced that Jacob was either joking with him, or that the device ran by magic. As Jacob pressed a button with a weird green symbol, Bowman watched the phone with eager curiosity. At least it was a momentary distraction from the fact that one of his best friends was almost a twentieth of his usual gigantic size.