The most common thing people say back to Walski when he asks this question is "between a lizard and what?". Well, allow Walski to repeat the question.
What's the difference between a lizard?
(the difference, in the full post)
The answer is:
One of its legs is both the same.
Yes, Walski is in a strange mood today... but Walski could easily have answered "42" and utterly confuse the hell out of you. There is a history behind this reptilian conundrum, but Walski won't get into it.