Granted, it is unlikely Cynthia is actually Krang. It’s more likely that she will be revealed to be some Utrom lieutenant doing experiments and readying the planet for Krang’s arrival. But she is still wonderful as a villain even without some connection to a better-known character. This is in no small part due to Cynthia delivering the single best joke in the movie.
For the entire film, we’ve followed and understood the Turtles’ longing for the human world, and also understood Splinter’s hesitance to let them go outside the sewer thanks to some very bad experiences with humans. Splinter fears that humans will not only kill his sons but specifically milk them for their blood, a terrifying thought despite the fact that — as the Turtles repeatedly explain — they don’t have nipples to be milked.
And yet, at a crucial moment when the Turtles are defeated by Superfly and his gang of mutants, they are found and captured by Cynthia’s strike force. Desperate to retrieve the ooze that created the mutants so she can use it to create biological weapons, Utrom orders the Turtles connected to the machine that will drain the ooze from them — literally a milking machine, named The Milking Machine.