Here is one I learned through a friend. I'll put the lyrics here and then follow with a link that also features the tune. As I learned it, it is generally sung while bouncing a child on one's knee. When arriving at the final "plumps" you suddenly straighten out your leg while holding tightly to the child, giving them a sensation of falling.

    Hoppa, hoppa Reiter

Hoppa, hoppa Reiter,
Wenn er fällt, dann schreit er!
Fällt er in den Graben,
Fressen ihn die Raben
Fällt er in den Sumpf,
Macht der Reiter plumps!

Now, this is as much as I learned. The verse was repeated to make the melody work, I believe. My poor memory was helped by the inimitable, Joe Offer. Here are the lyrics given at the wonderful, http://ingeb.org/

Hoppa, hoppa Reiter,
Fällt er hin so schreit er,
Fällt er von dem Pferde,
Liegt er auf der Erde,
Fällt er in das grüne Gras,
Macht er sich sein Pelzchen naß,
Fällt er in den Sumpf,
Macht der Reiter plumps!

Melody, etc. here.