Plot hole: If Marybeth was able to seal her nostrils and use her extended finger to remove the cap and make nobody suspicious about her, why didn't Delilah do the same thing? She was alien, so she should've still been able to do it, same as Marybeth.
Continuity mistake: When Casey and Delilah watch Nurse Harper get infected by Coach Willis from inside a closet, the closet's shutter windows switch from closed to open between shots.
Chosen answer: The Kids Aren't Alright - The Offspring.
Class of '99 - Another Brick in the Wall (Part 2).