Frog legs dance when salt is sprinkled on them
A frog’s muscles do not succumb to rigor mortis as quickly as most warm-blooded animals which makes it possible for the muscles to move post-mortem if energy is applied to them some how. This can be done either by cooking (heat/energy) or by salting (ions).
Salt,also known as NaCl, can work like electricity because it is made up of ions (Sodium and Chlorine to be exact) and ions carry an electrical charge. In living animals, sodium delivers a signal to cause muscles to contract.
The frog legs in the video are fresh so energy (ATP) is still stored in the cells. When the electrical impulse is applied, the legs contract even though the frog is dead!
Of course this doesn’t apply to only frog legs!