Rulers and their pets have long fascinated the public, from the King Charles Spaniel (bred since the 1600s) to our current president's Portuguese water dog. Portraits of the wealthy elite often feature the house pet—maybe a puffy Persian cat or toy dog.

Most presidents have kept a dog or a cat, but earlier Presidents had much more exotic pets. William Taft kept a cow on the White House lawn, the last among many presidents to do so. Teddy Roosevelt had a number of snakes; McKinley, a parrot; and Harrison, a billygoat. Lincoln kept a pig and a turkey, among other four-legged friends. (And—as far as dogs go—James Garfield named his dog "Veto.")

The Presidential Pet Museum does not exclude larger pets. George Washington's horse, Nelson, has an exhibit dedicated to him. Calvin Coolidge and his wife kept an astonishing number of animals for the First Family: many dogs, a donkey, a few canaries, a goose, and a bobcat, as well as lion cubs, a pygmy hippo, a bear, and a wallaby, given to them by foreign dignitaries. However, it is President James Buchanan who tops the list with a herd of elephants from Siam and a pair of bald eagles.

The latest addition to the South Lawn are the bees the First Lady keeps—she gives White House honey to visiting ambassadors—though she probably doesn't name them all. Bo Obama is named after Bo Diddley, the great songwriter and performer.