Usually it is very tedious to modify an animation if it has a lot of keyframes, since each keyframe has to be changed individually. With the "name your own price" extension KeyTweak you can easily modify all keyframes in the workarea at once. You can even fade the changes in- and out to avoid abrupt changes. In this animation tutorial you learn how to modify a bouncing ball animation with KeyTweak. But you can apply the same technique to any other animations that involve lots of keyframes.