In the beginning of the episode, the Challenger the kids were in is green. When the team shows up the car is blue.
When the female shape-shifter asks her 'target' for directions, he has unlocked, but not opened, his car door. When he offers to write them down, he closes the car door.
When Walter, Broyles and the team examine the dead bodies of the teenagers, it is twice mentioned that the victims have three prong holes in the soft palate. The part of the mouth where the holes are found is actually the hard palate or roof of the mouth. The soft palate is the soft tissue that hangs down in front of the throat, the uvula.
In the lab, Walter asks for car batteries, a voltage transformer, and a corpse. A regular voltage transformer would only work with alternating current, while the car batteries only supply direct current; hence, no transformation of the voltage would occur.
Peter mentions a Star Trek convention at the Worcester Centrum. This venue's name was changed to the DCU (Digital Federal Credit Union) Center several years ago.
When Thomas Newton makes a phone call to 911 from a payphone, he properly makes it without depositing money. (Emergency calls are free from payphones in the US.) However, when he hangs up the receiver, change is heard dropping through the mechanism of the phone.
When the first teenager is found dead, no one acknowledges the broken glass on the car. That would be the first indication to inspect inside the warehouse. The reason they take a look, is because of a joint without lipstick. Indicating that the dead girl wearing lipstick, wasn't alone.