Culture is such a massive topic and can be hard to define. L&D folk are often asked to help define, shape or change culture. Clearly, it can't be done quickly. EVERYTHING is intertwined, and it's hard for individuals to see how they can make a difference.
These two simple exercises can quickly and easily illustrate the effect that every single person has. Designed for Face-to-face delivery, though the second COULD be adapted for virtual if you use a shared whiteboard.