When given a sudden scare the muscles in the legs of the goats freeze up, the animal quickly topples over as a result and may lay there frozen for 10 seconds or so. For many years Myotonic goats were used as meat goats, intentionally scared so they would build up muscle in their leg from repeatedly freezing up. Now they are more likely to be kept as pets or occasionally for cashmere fiber that some produce in the winter.
Myotonic goats are also called fainting goats and are smaller goats, often black and white, but they can be any color. They are pretty easy to keep, needing shelter in cold and wet weather, and they are less likely to climb fences than other goats.
If bred to another goat the fainting gene is recessive. Younger fainting goats are more likely to fall over as the older ones learn how to brace themselves. Of course any animal that falls down when frightened may be an easy target for predators, or thieves. As such it is a good idea to keep your goats well fenced and secure.
Read here if you wish to learn more about goats and goat care.