Calvin Coolidge had a 'pet' pygmy hippopotamus named Billy, which was short for William Johnson Hippopotamus. However, this pet didn't live in the White House with Coolidge in his family, but rather resided at the National Zoo in Washington, D.C. Billy lived for about 30 years.
President Coolidge received Billy as a gift from a member of the Firestone family. The pygmy hippo was initially trapped in Liberia and brought to the U.S. as a gift for the president, who was known as a collector of exotic animals. Billy weighed in at more than 600 pounds and grew to be over 6 feet long.