A very simple gameplay mechanic, and if that were it all there was to it I probably wouldn't be talking about it here. What makes this game special is the manner in which Rubilon has implemented the scoring and the power-ups.
Simply hitting one target as it is walking by will score a measly 10 points. If you are lucky enough to hit more than one, a combo bonus of 25 points per each additional target hit is scored. The trouble with this strategy is you will soon run out of the 30 little people you begin the game with. The real meat of the gameplay is in hitting the same target again, and again, and again.
Hitting one target will send it running in the opposite direction from which it was walking. Hit it again, and it will again turn and run in the opposite direction, but it will now have a white glow around it. You have now earned an additional little person, and will earn another for each time you hit the target while it's glowing white. There is a maximum of 100 additional power-ups you can earn in a game, though earning even 50 proved difficult for me.
Analysis: This is a good example of a very simple gameplay mechanic made into a compelling and addictive (mini)game by adding a clever scoring and power-up structure. I like how simple and accessible the game is to pick-up and play, and yet how difficult it is to master. After playing over 20 times, I managed to reach only the "beginner" score rating of 5,000 points. It's difficult to imagine being able to score over 100,000 points, and yet the author clearly indicates that it is possible.
Babycal Throw is an exceptional mini-game design in an elegantly simple little package. Click.