Renders the collection twice.

app.js

define([
  'jquery',
  'underscore', 
  'backbone',
  'views/request',
  'views/new_request'
  ], function($, _, Backbone, RequestView, NewRequestView){
  var AppView = Backbone.View.extend({
		el: $("#request-app"),
		events: {
			"click button.new-request": "toggleNewRequestView"
		},
	  initialize: function() {
	  	this.listenTo(this.collection, 'all', this.render);
	    this.collection.fetch();
	  },
	  render: function() {
	  	this.collection.each(this.addOne);
    },
    addOne: function(request) {
    	var view = new RequestView({model: request});
    	this.$("#request-list").append(view.render().el);
    },
    toggleNewRequestView: function(ev) {
      if (!$("#new-request-form").length > 0) {
      	var view = new NewRequestView();
      	$(ev.currentTarget).after(view.render().el);
        $("#new-request-form").slideDown(function() { $(ev.currentTarget).text("Cancel"); });
      } else {
        $("#new-request-form").slideToggle(function() {
          $(ev.currentTarget).text($(ev.currentTarget).text() === "Cancel" ? "New Request" : "Cancel");
        });
      }
    }
	});
	return AppView;
});