I've noticed this behaviour and haven't been able to find anyone describing the same thing. One of my pigs loves cuddles and the other one (Shelley) not so much, so when I take the first pig out Shelley will do very fast laps of the cage and occasionally squeak. They are about 4 and a half years old. Does anyone else notice anything like this? I can't tell if she misses her cage mate or if she thinks she's being left out of a snack session. I don't think it's popcorning but I'm not sure.