Thumbelina, who weighs 4st 9lb, was born on a farm in St Louis, Missouri.
Her owners breed miniature horses but Thumbelina is a further quirk of nature - a miniature of a miniature.
She eats two cups of grain and a handful of hay each day.
Radar, at 6ft 71/2in from hoof to shoulder, is from Mount Pleasant, Texas.
At 2,400lb, he has a giant appetite to match, putting away 20 gallons of water a day and 18lb of grain.