What are the differences between normal version and director's cut version of episode 6?
According to the wiki:


  The uncut version of this episode features more explicity such as:
  
  
  More of Yoko's breasts are revealed. At the end of the episode, her top falls off completely-although we still don't see anything.
  Gimmy's penis is briefly shown. (This is actually not seen as taboo in Japan, as Gimmy is considered too young to be sexualized.) 
  
  
  Scenes added include:
  
  
  Kamina trying to peek at the girls.
  The beastmen fool Kamina into giving up Gurren-by offering to remove the pixellation seemingly covering their nudity. (Of course, they
  aren't actually naked-just wearing tiny, skin-tinted swimsuits.)
  The beastmen using a shock collar-like device on the girls.