When guinea pigs run back and forth across their cage and jump up and down repeatedly, it is because they are happy. This behavior is known as popcorning, because it resembles the motion of popcorn when it is popped.
There are two different ways that guinea pigs popcorn. They run and jump straight up into the air or kick their legs out as they jump so that they resemble a bucking horse. Guinea pigs also squeak when they popcorn. Popcorning is done the most by young guinea pigs that are also able to jump the highest, although adults still occasionally engage in this behavior.
Guinea pigs often popcorn when they are given a treat or when they are excited to see their owner. The rodents cannot be taught to replicate this activity on command but they are more likely to do it if they are happy with their living conditions. To make it more likely that guinea pigs popcorn, owners should provide fresh water, hay and crunchy vegetables; keep more than one guinea pig together in a cage; make sure the guinea pigs have enough room to sleep and exercise; check them over daily for any abnormalities; and fix problems quickly.