Bananas are Donkey Kong's main food of choice. He is overprotective of them and becomes enraged and chases people who take them from him.
Bananas first appeared in "A Monkey for your Thoughts?", in which Donkey Kong receives a message from Diddy Kong telling him two plumbers in overalls stole his bananas. Thinking them to be Mario and Luigi, he chases them everywhere until he receives another letter from Diddy informing him that it is really Wario and Waluigi. After apologizing to Mario and Luigi (though they refuse to forgive him), Donkey goes to get revenge on Wario and Waluigi, who end up regretting their crime as they scream in terror when Donkey Kong prepares to chase them.
A banana appeared in "Stupid Wario Brothers and No Snacks," where at the end, Wario and Waluigi are sitting on swings after a bad day. Wario finds a banana on the ground and sits back down, only to land on Donkey Kong's back, who proceeds to chase the terrified Wario Brothers.
In the episode "Snake VS Guard," Donkey calls Snake on his codec. When Snake asks him how he got his frequency, Donkey tells him he found it on the back of a CD case. Meanwhile, Donkey Kong is looking for his bananas and Snake says he thought he saw Otacon with some bananas. When Donkey asks him where he is, Snake tells him that Otacon is supposed to be in a nearby house; however, Otacon hasn't picked up his Codec calls in awhile. Snake asks Donkey Kong if he finds Otacon to tell him to answer his Codec calls. Later, Otacon goes to the toilet because of his stomach hurting. While being in the toilet, he is soon met by Donkey Kong.
At the end of The Interactive Adventure, Snake, who was unable to make funny jokes, finally manages to make Mario and Luigi laugh at his joke involving one banana. However, Wario (who is treated as a comic relief villain) beats with a joke involving two bananas, which angers Solid Snake.