"Close, but the answer to all three is a baby. True, it crawls around on four legs, but if you cut off it's arms, it'll squirm around on two. If you give it a crutch, it can hobble around on three."

My favorite answer to the riddle: "What walks on 4 legs, then 2 legs, then 3 legs?"

video game. The whole convo is below:

Doctor: The answer is man. We crawl on four legs as babies, then learn to walk upright, then as elders we use a cane.
Riddler: Close, but the answer to all three is a baby. True, it crawls around on four legs, but if you cut off it's arms, it'll squirm around on two. Then, if you give it a crutch, it can hobble around on three.
Doctor: That's horrible! How can you even joke about something like that?
Riddler: Easy... It's not my baby...