At the end of the BAIT episode when the team are around Tony's desk. The Slice of Pizza Tony is holding in his left hand changes between having a bite taken from it to a full slice and back again to a bite being taken.
Abby's leather collar/necklace changes between shots. The front switches with the backside (lock) when she has a discussion with McGee about Death Metal in Abby's lab.
When Gibbs gives Nadia her inhaler, she puts it in her mouth and you can hear it cycle twice. She never actually depresses the inhaler.
The rest of the team figures out that the people controlling Cody have eyes in the room after he asks Gibbs why he nodded while Cody's back was turned. They should have also seen Gibbs doing sign language before that and told Cody to ask about it.
The SRT and NCIS personnel would have access to laser microphones and thermal scopes, so they would be able to get eyes and ears in the classroom.
When Kody reiterates that the deadline is sunset, Gibbs asks, "which sunset: civil, nautical or astronomical?" In reality there is only the one sunset, which produces civil, nautical, and astronomical TWILIGHTS, when the sun is 6, 12, and 18 degrees below the horizon respectively.
Cody's father refers to the "SRT teams". As a Major, he would probably just call them "SRTs", since the word "Team" is in the acronym.