While the broad strokes of the turtles’ origin have been retained — a leaked mutagen covers the four turtles, who are then raised and trained in the sewers by their rat father/sensei Splinter — many of the details are different. This includes the introduction of a new villain, Eric Sacks (played by William Fichtner), who bioengineered the mutagen along with the deceased father of news reporter April O’Neil (Megan Fox), as well as the omission of Hamato Yoshi, the rival of Oroku Saki (AKA Shredder) and master of Splinter.