Too bad about Master Splinter, though... but this was very awesome. It is indeed darker. But that's why I love Newgrounds, there are always darker versions of movies about well-known characters here, such as Mega Man, Super Mario, Donkey Kong, etc. I have seen alot, but your stuff is the only one with the TMNT I've seen with darker plots and animations. I don't know why people haven't added so much TMNT stuff here, as it is popular too. Maybe there will be more one day?
Anyways, this was great. The music was great also. So fitting for a ninja (or four). You should do more. You have an amazing talent in animation.