Question: What goes on four legs in the morning, on two legs at noon, and on three legs in the evening?
Hint: What if morning, noon, and evening were a metaphor for young, middle-aged and old?
Answer: Man. He crawls as a baby, walks, then uses a cane in old age.
Question: My thickness is no more than a few centimeters, yet my depth can span to infinity. Although mundane, I intimidate most animals. When in my presence, you will inevitably follow me. What am I?
Answer: I'm a mirror.