alien theme is faster than a lot other themes. Why? It updates part of the prompt asyncronously - the time consuming processings like git status checking, git dirty copy checking etc. How? It starts a background job for these process, and in the mean time draws initial prompt and lets you use the terminal as you would normally. alien theme is independent of any library like Oh-My-Zsh or Prezto. Whatever it needs already included inside. The only exception is font. You need to install the powerline patched fonts to properly display the prompt.