What Is That Dramatic Noise Heard After Each Act?

The show creator, Donald P. Bellisario, made the noise that distinguishes the beginning and end of each act using a microphone.

Mark Harmon Wears T-Shirts Made For Him By His Fans

Harmon, who plays Leroy Jethro Gibbs, is known to still wear t-shirts that were sent to him by fans over the years. He’s said to lounge around the house in authentic vintage Marine Cops and NCIS t-shirts.