You know he's in there. And he does not want to be disturbed. But you want to disturb him! One knock might not suffice. It will require many. And you want to not be present when he is disturbed to the point of answering the door, because he might be moving fast enough to see you bolting away, and
chase you, and catch you.
The Sophomoric division of BUNGCO (ok, that is most of it) is proud to present the Automated Door Knocker. Often the ADK will be destroyed after a single use, and so we keep it cheap: a wind up timer spring with a notched cardboard disk and a knocker. Affix it firmly to the door or adjacent substrate. Wind it up. As the timer turns, knocks will be delivered according to notches in the disk. Prepunched disks can deliver a steady "water torture" tapping, a flurry followed by some slower knocks, or "shave and a hair cut" followed by a much delayed "two bits". Or punch your own! Larger disks can deliver a long and unrepetitive variety of knocks, and BUNGCO offers the Neal Peart ADK boxed set of prepunched solo disks for the true aficionado.
The knocker is a simple rubber ball, which can be substituted for a white gloved cartoon fist, a raven, or whatever else you can jam onto the knocking rod and make stick.
Now disturb with knocks to your hearts content, and without fear! The true beauty: when the disturbed answers the door and sees that his visitor is actually a floppy machine mounted marital aid trying to gain entrance by virtue of jazzy rhythm riffs. His heart will be light! And he will take down the ADK gently and save it for his own reuse at a later date. It is better to give than to receive. The Great Circle of Life.