1. A way to describe someone's behavior when they are being crazy, insane, silly, spontaneous, funny, or wild.
Whenever Alexis and Nate hang out together, they are coo coo banana sandwiches!
The act of cumming on someones ass cheeks and then eating the butt out.
Joe: "Hey guys we need an example of a banana mayonnaise sandwich"
Aidan: "I really like that banana mayonnaise sandwich"