Well, you were nearly right, they are called 'Cuy' and they are a relative of our piggies. There are some in this country, but they are few and far between as they are not for novice pet owners.
They are a lot more 'primative' than our cavies, and crepuscular which means they are active at dawn and dusk and like to hide at other times. They are very strong and can run extremely fast, they don't really climb like normal piggies, but can jump vertically!
A lot of these Cuy are polydactyl, so they have more than the normal number of toes on each foot, in fact the purer the line, the larger number of toes they can have - therefore they do normaly have very large feet
. They also have a shorter life-span - something which is fairly common in giant sized animals.
You are not likely to find any in pet shops (thank heavens), as there would be awful consequences if a Cuy boar mated a normal sized cavy sow - she just wouldn't be able to carry the babies! That said, the normal weights of baby Cuy can be around 110g - 180g. They are quite popular in Europe as i believe they can be shown over there but not here.
Alison