What is Nate The Snake Joke?

In a large and almost deserted desert, there lives a snake. His name is Nate, he is, Nate the Snake. His one mission in life is to stop a lever from being pushed because if it is, the world will end.
Now, Nate has been the desert’s only inhabitant for a while, so he has never had a friend. Then one day, someone else moves into the desert, this person’s name doesn’t matter, so we’ll call him Trevor. Now as they are the only two living beings in the desert, they end up spending a lot of time with each other. So after a while, they become really good friends.
One day when Trevor is over at Nate the Snake’s house, he wanders over to the lever and is about to pull it just to see what it does. Then suddenly, Nate shouts “Don’t pull that or the world will end.”, Trevor reacts quickly so he doesn’t end up pulling the lever.
A few months, Trevor buys a used car and is driving it over to Nate’s house to show it to him. As Trevor approaches Nate’s house, he sees that Nate is in the middle of the road sunbathing while listening to music. At this point, Trevor’s car’s brakes then fail so he can only turn away from Nate and hit the lever, which would cause the world to end, or run Nate over. In the few brief seconds that Trevor has to decide he chooses to hit Nate in order to preserve the world’s safety.
A few weeks later, when Trevor was driving to Nate’s funeral he was having doubts about what he had done, but he arrived upon the conclusion that it was better Nate than lever.