Revealing mistake: In the part where Rahzar grabs Mikey by the arms and begins swinging him around at the concert, look at Mikey's shoulders. You can see the material of the actor's body suit folding at the shoulders as it is bent further than it was designed for. (01:08:15)
Quantom X
Revealing mistake: In the junkyard, Leo and Raph grab a long pole and plough through several Foot Ninjas with it. It is painfully obvious the ninjas react to the pole before it ever hits them. Especially the guy on the ground. (00:53:20)