Ticklish Rock is an unusual sandstone formation in Shrewsbury Township, Sullivan County, Pennsylvania, perched on the rim of the Allegheny Ridge beside a steep cliff. Part of Pennsylvania’s Catskill Formation, it was originally laid down in the Devonian period, but its current hammer-like shape developed much later through differential weathering. That erosion stripped away surrounding material and left a broad brown-and-green block balanced on a much narrower pedestal. The main block is about 3 feet high, 8 feet long, and 6 feet wide, while the base is only about 18 by 30 inches, making it a striking example of erosion creating a distinctive natural landmark.