During our undergrad years, my now wife, and then fiance KK had a small inner circle of housemates, Kristine, Kate, and Lisa. Kristine worked in a local used bookstore, and often brought home surplussed pulp fiction and romance novels - the ladies had a sort of hobby of reading the spicy portions aloud.
Long story short, one of the novels described, among other topics, a young woman demonstrating her sexual talents by using a ripe banana as a dildo. Her objective was to demonstrate certain sexual capabilities to a very demanding lover. She was first required to manipulate the banana hands-free, relaxing her labia sufficiently to allow the banana to fully penetrate her, without crushing or breaking it. Once her cunt was full of whole ripe banana, the next task was to slowly, carefully eject it, whole, without crushing it. And so on...
The girls were fascinated by, fixated on this scene, and actually started practicing it with one another. To this day, KK still calls it the "banana trick" - whenever I hear those two words together, with a certain lilt in her voice, my cock gets rock-hard.
Then, the sight of those three lithe young women, trying to role play that scene was ball-exploding.