A function that forks a Gist. You can use this to fork your own Gists.

fork-your-own-gist.js

function forkGist(user, gist) {
    var path = (arguments.length ? ('/' + user + '/' + gist) : location.pathname);
    var form = document.createElement('form');
    form.method = 'post';
    form.action = 'https://gist.github.com' + path + '/fork',
    form.submit();
}

// Paste into browser console when viewing a Gist (including your own) to fork it
forkGist();

// Fork a Gist from anywhere
forkGist('prettycode', 5409158);