If your guinea pig is running around and jumping suddenly in the air, then you’re seeing a behavior known as ‘popcorning’. It’s a very entertaining movement that’s more often seen in juvenile guinea pigs, but adults are perfectly capable of popcorning too.
'Popcorning' is a sign of contentment
Popcorning is the result of a very happy guinea pig, so if you see this then there is no cause for concern - it’s actually an extremely good sign. The most likely circumstances in which your pets will popcorn is if they’ve been given fresh hay or one of their favourite foods. There is no way to encourage your guinea pig to popcorn other than take excellent care of it as normal. Many owners are very lucky and see this behaviour often.