In Worrals of the Islands, Uleef was the name of a Dutch planter who lived on the Indonesian island of Java. He escaped from Java when it was occupied by the Japanese and sought refuge in a village on a small island. However the village was attacked by Japanese sailors from the Tamaroa. As he was sick with fever, he could not escape into the jungle to hide. His friend Jan Vandergroot, another planter, stayed with him. Both were captured by General the Prince Samurai, the local Japanese commander. He wanted to behead them but Worrals and her party attacked, scattering the Japanese troops and capturing the General.
Uleef's name is also given as "Kleef" on at least one occasion in the book. The Aredit comic strip adaptation Quand vient la mousson also gives his name as "Kleef". However the name "Uleef" occurs at least twice in the book and so is unlikely to have been a typographical error.