The portrayal of hyenas in The Lion King led to several researchers, whose work was with hyenas, to boycott the movie. One such researcher actually sued Disney for the defamation of hyenas. The fear of the researchers was that in casting the hyenas in the role of evil (and stupid) minions of Scar, their efforts to preserve the lives and populations of hyenas might be compromised.
Another controversy involves the similarity of The Lion King to a Japanese show called Kimba the White Lion. Many of the scenes and shots used in The Lion King were very similar to the Japanese show. In the end, the Japanese studio decided not to sue because of the quality of Disney's lawyers, although there was some speculation about Disney paying them to keep quiet.
Interestingly, The Lion King was not expected to do well on the big screen. Many invited to participate in its production rejected the opportunity stating reasons ranging from a poor plot to a preference to work on Pocahontas, which was expected to do considerably better than the Lion King. The Lion King, in spite of initial low expectations for the film, was the most successful animated picture of its time. More importantly, it also holds a place in the heart of many people; it is a part of their childhood.