CreativeQuestionsType.php

<?php

namespace JStout\MainBundle\Form;

use Symfony\Component\Form\AbstractType,
    Symfony\Component\Form\FormBuilder;

class CreativeQuestionsType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {

        $builder
            ->add('question', 'entity', array(
                'class' => 'JStout\MainBundle\Entity\Question',
                'query_builder' => function($repository) { return $repository->createQueryBuilder('q')->orderBy('q.question', 'ASC'); },
                'property' => 'question'
            ))
            ->add('pos', 'integer');
    }
}

CreativeType.php

<?php

namespace JStout\MainBundle\Form;

use Symfony\Component\Form\AbstractType,
    Symfony\Component\Form\FormBuilder;

class CreativeType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('name')
            ->add('title')
            ->add('description')
            ->add('body')
            ->add('script')
            ->add('creativeQuestions', 'collection', array(
                'type' => new CreativeQuestionsType(),
                'allow_add' => true,
                'allow_delete' => true
            ))
            ->add('active');
    }

    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'JStout\MainBundle\Entity\Creative'
        );
    }
}