Was on a Skywest UX (CR700 - sitting in F) flight yesterday. During boarding a TSO boards and walks to back of the plane. The captain notices and asks the FA "what's he doing? how did he get on my plane?". The captain keeps his eye on the TSO the whole time (for obvious reasons; TSA agents are known to damage planes), and rolls his eyes as the TSO leaves.

Evidentially airline pilots are unaccustomed to TSO pre-flight inspections.