Mongoose populate an array

gistfile1.js

var mongoose = require('mongoose'),
	Schema = mongoose.Schema,
	ObjectId = Schema.ObjectId;

mongoose.connect('mongodb://localhost/testy2');

var UserSchema = new Schema({
	name: String
});

var MovieSchema = new Schema({
	title: String,
	tags: [new Schema({
	    _name: {type: Schema.ObjectId, ref: 'Tag'},
	    _owner: {type: Schema.ObjectId, ref: 'User'}
	})]
});

var TagSchema = new Schema({
	name: String
});

var Tag = mongoose.model('Tag', TagSchema),
	User = mongoose.model('User', UserSchema),
	Movie = mongoose.model('Movie', MovieSchema);

User.create({name: 'Johnny'}, function(err, johnny) {
	Tag.create({name: 'drama'}, function(err, drama) {
		Movie.create({'title': 'Dracula', tags:[{_name: drama._id, _owner: johnny._id}]}, function(err, movie) {
			
			Movie.findById(movie).populate('tags._owner').run(function(err, movie) {
				console.log(movie.tags[0]._owner);
			});
		});
	});
});