In Keen: Galaxy, episode 4, go to the level entitled "Pyramid of the Moons,"
and from there, to the half moons painted on the floor.  If you stand on
these and do nothing for a while, Keen will moon you, instead of his usual
idle activity of reading a book.  This will only happen once per game,
however.

Also, in all episodes of Commander Keen, signs are written in an alien
language.  The comment is made, "too bad you don't know the language."  Well,
now you do.  The language is a simple symbol substitution, the key of which
is given below.  This key appears only twice in all the Keen games; in the
secret areas of the secret levels of episodes three and six.

  A     B     C     D     E     F     G     H     I     J     K     L     M
  #    #     #    ####   # #  #####    #   ###    #    #      #    #     # #
 # #   #                 #             #          #           #    # #     #
 # #   #     #    ##     #    # # #  ###   ###         # #  # # #  #       #
 #      #     #     ##   ###           #    #     #           #    # #   ###
 #    ####    #                        #    #     #    #      #    #
##

  N     O     P     Q     R     S     T     U     V     W     X     Y     Z
 # #   ##    # #    #          #     ##           #         #  #   # #    #
   #     #     #         # #   #      #    # #   ###    #     #    # #   # #
   #     #   # #   ###          #     #                      #     # #   # #
  #     #    #     # #   # #    #         #####  ###   # #  #      # #   # #
 #     #     # #   ###          #     #