Bananas (or Cave Bananas in the base game) are FoodItems found on Cave Banana Trees. These trees grow underground and will regrow after 4 days once picked. Splumonkeys will pick Bananas from Cave Banana Trees on sight, which has no effect on the 4-day regrowth period of Bananas. Splumonkeys also are more likely to follow and steal from a player if the player is carrying any number of Bananas.
Cooked Bananas are the product of cooking a Banana over a Campfire, Fire Pit, or Star. Like most fruits and vegetables, cooking increases the Health bonus slightly while decreasing the spoil time.
In the Shipwrecked DLC, Bananas take on a more yellow appearance. They are dropped by Jungle Trees when the trees are cut down therefore are easier and safer to obtain than their underground counterparts. They also have a chance to be dropped by the Slot Machine when three carrots are rolled. Bananas can be used to cook Banana Pop; can be added to the Crock Pot as Fruit fillers and are worth 1 fruit value. They are required to craft Silly Monkey Balls and Prime Ape Huts.
Additionally, Bananas are eaten by Prime Apes and can be fed to them to befriend them. Wilbur gains 10 when eating Bananas.
The Cave Banana is one of the few items in the game with examination quotes for Wilbur.
The raw image for the Banana shows multiple bananas in one bunch, but the Cooked image shows only three, which seem to be poorly prepared. This could hint to poor cooking/preparation due to abnormal food.
Wickerbottom's quote mentions that all of the bananas are genetically identical. This is probably a reference to the concern from botanists over the increase in cloned banana trees which could theoretically make them infertile. This could also be the reason Cave Banana Trees cannot be grown by the player.
The Cave Banana name is possibly a play on one of the most common banana cultivars, Cavendish Bananas.