flash
Explanation
The Joke
A person asks The Flash, the famous DC Comics superhero, whether he has super speed or super "everything fast." The Flash replies that it is just super speed. The questioner then asks, "Then how do you control your legs fast enough to maintain the correct biomechanics needed to keep running?" The Flash is stumped: if only his legs move fast but his brain processes at normal speed, he should not be able to coordinate his movements at super speed.
The Flash then admits he has a "second brain" -- a smaller neural cluster that sends signals to his legs. The questioner points out: "I mean, I don't know much about Flash lore, but..." and the final panel has someone saying "Remember, kids: different doesn't mean worse," implying The Flash basically just admitted to having some kind of strange extra nervous system in his lower body, which is being charitably described as "different, not worse."
The Humor
The comedy comes from applying real-world biomechanics and neuroscience to a superhero whose powers are meant to be accepted without scrutiny. The joke dismantles the Flash's powers by asking a simple, logical question: if you only have super speed in your legs, how does your normal-speed brain keep up? The Flash's improvised explanation -- a second brain near his legs -- only makes things worse, turning a cool superpower into something that sounds like a medical oddity. The final "different doesn't mean worse" panel plays it as if the Flash has just revealed an embarrassing disability, adding a layer of comedic pity to what is supposed to be one of DC's most impressive powers.