With one ex, he introduced me to his friends as his girlfriend about 2 months after we started dating, I was "WTF?"...I was definitely caught off guard because previous BF's had asked, ahead of time.
Last ex, he asked me the first date was I seeing other people and then in about 2 weeks, he was all nervous, and started out with, "I know I may not have a right to ask you this, but, I'm not dating other people and I don't really want you to date other people..." It was sweet.