HOVEDSTADEN, DENMARK – Copenhagen’s Little Mermaid statue celebrated her 100th birthday Friday with parties for children as well as grown-ups, illustrating the universal appeal of Hans Christian Andersen’s poignant fairy tale.

Perched on a rock in the water just off the star-shaped Kastellet fortress near the city’s harbor, the small bronze-skinned sculpture has become a Danish icon on a par with Carlsberg, the brewery once owned by the man who financed it.

Today, millions of children know the Little Mermaid from the Disney movie and the merchandise it spawned, but the original story lacks the happy ending of the animated film....