A person who acts in a confusing or bizarre manner. Can be used to describe someone, or as a one-word response. Despite the "fellow" suffix, usage is unisex.
1) After she stormed the cafeteria naked and covered head to toe in red paint, I always thought Taylor was a bit of an oddfellow.
2) person one: I think Dobby was a better CGI character than Gollum.
person two: oddfellow.