Gumball and Darwin were walking thru the mall when all of a sudden a random naked man jumped out at them and raped both of them. The two ran to the police who didn't care about the events. Then the two brothers had to find a way home so they can kill themselves out of guilt.
They hitched a ride with a friendly trucker who brought both of them home where they processed to tie a noose. Gumball's sister decided to help them kill themselves by bringing in a chair for both of them. She also wrote both of them suicide notes.
Both the brothers got up on a chair and then kicked it out from under them. Gumball easy died but Darwin survived because he had no neck. Darwin was able to reproduce and pass on his genetic ability of not having a neck to his offspring making him physically fit thus proving the "Darwin theory of evolution".