I created a colorful diffy sheet for a manila folder center.
To work a diffy, you start with the four corners and fill them in with any two digit numbers. Then you subtract the numbers in corresponding corners and write the answer in the middle. Then, turn the diffy! You have new corners to subtract. You will keep subtracting until the entire thing subtracts down to 0's.
My students always liked seeing how many levels of subtraction they would do before it turned into 0's.