For the Last Time!
Allow us to preface this by saying that Frankenstein isn’t the name of the monstrous creation. Dr. Frankenstein was the mad scientist who created his monster, which simply goes by Frankenstein’s Monster. Alright, now that you’re caught up, you can read the joke.
Get it? Dr. Frankenstein entered a body-building competition and completely misunderstood the objective. He wasn’t supposed to build a monster, but he was supposed to bulk up like Arnold Schwarzenegger! Everyone got the joke except for the commenter who, for the last time, wanted to explain the obvious. This is one of those r/woosh moments that will be immortalized in the annals of Reddit.