How to Extend Twitter Bootstrap Plugin?

This is an old thread, but I just made some custom extensions to modal using the following pattern:

// save the original function object
var _super = $.fn.modal;

// add custom defaults
$.extend( _super.defaults, {
    foo: 'bar',
    john: 'doe'
});

// create a new constructor
var Modal = function(element, options) {

    // do custom constructor stuff here

     // call the original constructor
    _super.Constructor.apply( this, arguments );

}

// extend prototypes and add a super function
Modal.prototype = $.extend({}, _super.Constructor.prototype, {
    constructor: Modal,
    _super: function() {
        var args = $.makeArray(arguments);
        _super.Constructor.prototype[args.shift()].apply(this, args);
    },
    show: function() {

        // do custom method stuff

        // call the original method
        this._super('show');
    }
});

// override the old initialization with the new constructor
$.fn.modal = $.extend(function(option) {

    var args = $.makeArray(arguments),
        option = args.shift();

    return this.each(function() {

        var $this = $(this);
        var data = $this.data('modal'),
            options = $.extend({}, _super.defaults, $this.data(), typeof option == 'object' && option);

        if ( !data ) {
            $this.data('modal', (data = new Modal(this, options)));
        }
        if (typeof option == 'string') {
            data[option].apply( data, args );
        }
        else if ( options.show ) {
            data.show.apply( data, args );
        }
    });

}, $.fn.modal);

This way you can

1) add your own default options

2) create new methods with custom arguments and access to original (super) functions

3) do stuff in the constructor before and/or after the original constructor is called