Thimbletack

In British folklore, a brownie is a small being who secretly looks after a house. Treat it badly and it becomes a boggart that torments the people living there. Thimbletack is both: a loyal caretaker of the Spiderwick estate who loses control when crossed.

In old tales, a brownie works at night in exchange for a bit of food left out for him, and leaves if anyone tries to pay him with clothes. That's why Thimbletack is so touchy: one wrong move is enough to turn the house upside down.

In the movie, Thimbletack has guarded the house and Arthur's Guide since 1928. When Jared opens the book, he flies into a rage, turns boggart and wrecks the house, and the kid takes the blame. Only honey turns him back into the gentle brownie. From then on he's a grumpy ally who keeps warning that the Guide is dangerous. To him, the Graces are intruders in a house he's protected for decades, and every misplaced thing is an insult.

When the kids go to the sylphs' realm after Arthur, the Guide seems lost. But Thimbletack had swapped the pages beforehand, so the real book is still with the Graces. The brownie's quick thinking keeps the Guide out of Mulgarath's hands, at least for now. It's not the last time the grump proves he's on the kids' side.

In the 2024 series, Jack Dylan Grazer voices him. Thimbletack is the boggart who shows Jared that magical creatures are real. For the kid fresh from Brooklyn, it's the first sign that the Henson estate holds far more than it seems, and the start of the hunt for the pages of Arthur's guide.

In the movie, Martin Short voices him, giving the brownie a nervous, chatty edge. In the series, Jack Dylan Grazer, Eddie from It (2017), takes over for a new generation. In both versions, Thimbletack is the first creature the Graces meet and the bridge between the family and the estate's hidden world. He trusts no one, but once he picks a side, he sticks with the siblings.

In the books, no honey needed: being kind to Thimbletack is enough to turn the boggart back into a brownie.