As a Great Dane, Rocko was already going to be big. But his owners didn't expect him to be this big.
"We didn't realize he was going to be so big. He was so big. Is he half Dane or half pony, what's going on here?" Nicholas Helms, one of Rocko's owners, told KOLO in Reno.
Rocko, of Sparks, is in the running for world's tallest dog, standing 40 inches from paw to shoulder and more than 7 feet tall when standing on his hind legs.
He's only 2 years old and his owners told KOLO he was the size of a 6-month-old Labrador at 8 weeks. Rocko hasn't stopped growing since.
Helms and fellow owner Jessica Williams have submitted Rocko as a contender for the Guinness Book of World Records as the tallest living dog. Before him, the tallest dog on record was a 44-inch Great Dane from Michigan named Zeus, who died in 2014.