The primary theory being tested was that the center of three creatures would receive the most click-thrus, with the creature on the left coming in second.
There were some secondary theories regarding alignment, but I never got enough clicks to make sense of them. I guessed that the creatures would be good, evil, and neutral, from left to right.
The clicking theory proved to be correct, but we never got to see any alignments, as people lost interest in clicking on tiny animals, long before then.