When going after the monster Manuel, the characters step in the slime trail he left behind, making squishy sound effects. Despite this, there are no tracks left in the slime, no slime tracked through the halls, and no slime on their shoes afterward.
When Liz wants to turn out the lights, but the light switch is on Danny's side of the room, she simply unscrews the light bulb. The bulb is not hot to the touch despite having been on during their entire conversation beforehand.
Liz sees Danny looking at her during the pop quiz and turns her screen away from him, but the screen's side was visible to him previously and her moving it made it so that the front was visible to him.