Plot hole: When Freddy causes Carlos' hearing aid to be incredibly sensitive to the slightest sound, the sound of water droplets and pins falling is exceptionally painful. However, the sound of Carlos speaking or even Freddy's shushing him doesn't cause any discomfort despite those sounds being vastly greater than the previously mentioned sounds. (00:36:15 - 00:37:19)
Plot hole: The pipe bomb that Maggie uses to kill Freddy is the same one that was found in Spencer's room earlier in the film. It's already been established that Freddy was erasing the people he's been killing from existence, so that pipe bomb wouldn't be there to use on Freddy.
Answer: "Son of a hundred maniacs." Freddy was conceived when his mother, Amanda, was accidentally locked in a ward of violent mental patients and gang raped.
Brian Katcher