M. Night Shyamalan initially had a different concept for the "Those We Do Not Speak Of" Creatures. They were originally conceived to be monsters similar to the rock drawings featured at the beginning of the movie: similar to a Lion walking on its hind feet, complete with shaggy mane. When the creatures were built to full scale and brought on set, M. Night Shyamalan felt that the design was completely unbelievable. The creatures were quickly redesigned, most noticeably with the addition of the red cloak.
I know we've talked about it before, but I never heard all of these deatils: "similar to a Lion walking on its hind feet, complete with shaggy mane". I wonder if they ever took any pictures of these monsters and if they could be found on the net.