While not given a number, it seems that one of Gibbs' rules is to never bypass the chain of command. When Ziva asks if there are any more of "these rules," Gibbs replies "About fifty of 'em."
In the scene where Timothy McGee is looking for Jerry Smith's cell phone records (about 13 minutes into the episode) the camera shows names displayed on the computer. The name below Jerry Smith or Smith, W & J is listed as Murray, Chad. Chad W. Murray is the name of the stepson of show creator Donald P. Bellisario and the brother of Sean Murray, the actor who plays McGee.
When Ducky is doing the autopsy on Jerry Smith he is supposed to use the "scissors" to cut the ribs apart in order to get a better look inside his body. However as he is chopping it is clearly visible that he is in fact cutting nothing and just opening and closing them to make it look like he is.