Closet Programmers are similar the UnknownProgrammer, but not always heros.  They don't show up on mailing lists, they don't release their code, they don't publish their works. They hide in the closet. Some become very skilled after several years and end up surprising the community with a huge work and huge release. Others do not have a huge work or huge release they are hacking away at in the closet - rather they are simply lurkers, learners, meek, humble, quiet people.