Keystone Cops effect in FCP 7

well silent movies were usually shot at 18 fps (as opposed to 24 fps for sound films) so when projected in later days at 24fps, the material appeared sped up and in addition in the early days the cameras were hand cranked. "undercranking" meant action appeared sped up when projected, so speeding up your video may help.

Not sure what you mean by "keystone cops effect." Do you mean you want to make the clip contain plenty of slap-stick humor? Do you mean frame rate, like Michael referred to? Do you mean visually such as sepia toned or scratched looking? Some of the above? All of the above? Please be more specific.

-DH