Easily disable plugins and switch to a default theme using query strings.
Currently this plugin needs to be installed to the mu-plugins directory.
Once installed, add the query string ?theme=<number|theme_name> to the end of the url to switch to a default theme if using a number, or a named theme (e.g., ?theme=0 or ?theme=headway).
For disabling plugins, you would add ?disableplugins=1 as a query argument.
You can use these both at the same time too! You would add the following at the end of a URL: ?disableplugins=1&theme=0.