The Halloween Mash-Up pack from 2015 does not work as a standalone texture pack anymore.

In a regular world with the pack enabled (not the official template world), a lot of the textures are broken, including the custom crosshair, which flashes in split-screen. A lot of the mobs do not have a texture anymore, and the sky has lost its yellow hue. It’s very disappointing because this is my favorite pack!! For our world specifically, the cows and pigs had vanilla textures, but the villagers and cats were fine.