While Burger King’s Whopper was introduced in 1957, the Whopper Jr. didn't exist until the early '60s. The Whopper Jr. was actually not planned at all; it was invented completely by accident in a single day by a man named Luis Arenas Pérez in Puerto Rico.

In 1963, Pérez opened his own Burger King franchise in Carolina, Puerto Rico, but realized the bun molds for the Whoppers wouldn’t arrive in time for opening day. Pérez decided to use the molds for the regular hamburger buns but still use the same ingredients as the Whopper.

Pérez's mini Whopper was such a big hit that it was ultimately added to Burger King's official menu as the Whopper Jr. The Whopper Jr. is almost exactly half the size of the standard Whopper, according to Burger King — perfect for those intimidated by the Whopper’s size.