2 pipe cleaners + 1 handful of Fruit Loops (Cheerios or other circle cereal works as well = a colorful, crunchy and bendable caterpillar
After gathering your materials, decide if your caterpillar will have random colors or a pattern (we usually do a pattern to add a bit of math to the equation). Then, start stringing them on one of the pipe cleaners.
P.S. We usually do this activity near snack time as we end up munching as we go.