Introduction of Kobra into the DCAU.
This is Agent Bennett's only appearance that does not involve Zeta.
Although Agent Bennett explains what Kobra is, Batman should already be familiar with them, as it is later shown in "Unmasked" how he faced them around the time he was just starting out.
Introduction of False Face into the DCAU. The character had previously appeared in the live action Batman TV series from 1966.
While the real-life NSA are just a signals intelligence agency, in the timeline of Batman Beyond and The Zeta Project, they are consistently shown as an all-purpose counterterrorism force.