Bobby's grip on his knife rapidly go from overhand to underhand in different camera angles in the two against one fight.
The lockers behind Sam go from partially open to shut at various points during the confrontation with Samuel, most notably during the "You fed us to Crowley."
Bobby should not have been introducing himself to the locals as "Special Agent" Willis. In previous episodes he has always pretended to be Assistant Director Willis, the supervising agent for whichever FBI alias Sam and Dean were using at the time. So he should have been introducing himself as "Assistant Director Willis" or "AD Willis" for short; an AD would not be addressed as "special agent" as they outrank special agents.
When the group determines that the worm is weak to electricity, they opt to shock themselves to confirm they're not infected. The wire they use contains all three AC leads (live, earth, and neutral). Binding the three together would cause a dead short and instantly blow a fuse, therefore being totally useless.