Philadelphia Zoo bringing back iconic Zoo Keys

The Philadelphia Zoo is bringing back its iconic Zoo Key.

The plastic keys, shaped like different animals, will return in April. They will unlock book-shape boxes throughout the park with prerecorded stories from zookeepers and "insider secrets" about the animals.

Shaped like an elephant using its trunk to unlock the talking story box, the original keys made their debut in Philadelphia in 1960. Other animals, such as lions, were made into keys in subsequent years.

The keys were available for purchase at the zoo for nearly 50 years and were offered as educational prizes to schoolchildren until 2007, when the park ended the program.

Zoo officials say the old keys will work in the new boxes. Those needing keys can buy them for $3 at the zoo.