Answer: Pumpkin pi
It's October already and you know what that means: everything is pumpkin flavored. Pumpkin pie, pumpkin bread, pumpkin donuts, pumpkin spice latte, pumpkin ale, pumpkin soup, pumpkin cheesecake, and most importantly... pumpkin puns.
Explanation for the kids (and bad puns)
The Greek letter π (pi) is a constant value used in math. It represents the ratio of the distance around the outside of a circle (circumference) to the straight line distance from each side through the center (diameter). If you had strings the same length as a circle's diameter, this ratio would be the number of those strings you would need to wrap around the outside of the circle.
While the actual decimal value is a fraction over 3, that fraction goes on forever: 3.141592653589... Mathemeticians have calculated it to trillions of decimal places and still not found any end or pattern.
If you were to perform the same math on the size of a pumpkin, you would end up with a pumpkin based pi. Though the "pie" equivalent would probably taste much better.