Answer: Kitchen Sponges

In the original 1960s Batman television series, the first version of Batman’s iconic utility belt was, despite what an integral part of the whole Batman motif it is, quite a low cost prop.

How low cost? In the early episodes, the pouches on the utility belt were kitchen sponges glued to the belt with a faux strap glued to the bottom. Viewers at the time, thanks to the low resolution of standard television broadcasts and the significant phosphor fuzzing in old CRT televisions, didn’t notice. Later, when the show’s budget increased, they revised the belt to feature pouches made of actual leather.

When viewing the remastered footage today on a modern screen in much higher resolution, however, the pouches are very visible as exactly what they are: sponges, complete with the bumps and holes you’d expect.