Annual Donkey Kong Challenge
From the Super Mario Wiki
The Annual Donkey Kong Challenge is an event on the Donkey Kong Country television series. It is unknown when the challenge was started, although it is presumed that it began some time after Donkey Kong found the Crystal Coconut. According to Cranky Kong, the event is designed to keep Donkey Kong on his toes, and to prove that he will be a good ruler when he becomes the ruler of Kongo Bongo Island. If he ever loses, Donkey Kong must give up his claim as future ruler (and the Crystal Coconut) to whoever manages to defeat him. However, as Diddy Kong mentions, no one actually ever attempted to challenge Donkey Kong, due to his enormous strength.
The challenge was featured prominently in the episode Kong Fu. In this episode King K. Rool hires the titular character, Kong Fu to challenge Donkey Kong, in an attempt to win the title (as well as the Crystal Coconut) from Donkey Kong.
The match eventually ends in victory-by-forfeit for Donkey Kong. A solar eclipse (which had been predicted earlier in the episode) occurred during the match and Kong Fu (because of his severe nyctophobia) is unable to fight. Donkey Kong refuses to attack his enemy while he is paralyzed with fear, causing Kong Fu to gain a new respect for him. Kong Fu then forfeits the match (due both to his new respect for his enemy, and the fact that his fear was mocked by King K. Rool and his henchmen) making Donkey Kong the victor.