Yes, there have been Ninja Rangers before, but not like this!
When the Turtles got the Rangers' Power Coins in Mighty Morphin Power Rangers/Teenage Mutant Ninja Turtles, that left the gang from Angel Grove powerless... but not helpless. With Tommy being held hostage and the new Mighty Morphin Turtle Rangers busy fighting one of Rita's monsters in Times Square, the kids were anxious to do something. Enter Splinter, to give them a caring yet rousing speech, and also some loaner weapons:
In a better world, creating toys would be more affordable, and Hasbro would have been able to make this sub-line more than four releases (heavy on the re-use). Imagine: each set featuring one Morphed Turtle, and one de-powered Ninja Ranger!
Simone di Meo designed some awesome costumes for the kids, and they'd have been super cool to get as toys.