When discussing the propellants used by the jet-pack, McGee states that the use of Hydrogen Peroxide and Kerosene as fuels is highly unusual. This mix of fuels was used extensively by the British between 1955 and 1971 for a number of very successful rockets, culminating in the Black Arrow space launch vehicle.
In the elevator, McGee intimates to Gibbs that the jet pack was made by Bell Labs. That's the wrong "Bell". Bell Aerosystems was the developer.
Dr. Mallard tells Gibbs that Palmer is about to start his first "solo autopsy". But Palmer is working on a squirrel. Autopsies are only performed on humans - for animals the procedure is called a necropsy. A scientist as thorough as Ducky would surely know the difference.
Jimmy references encountering brown and black squirrels in the DC area. There are black squirrels but there are no brown ones. The other variety found in the area is the gray squirrel, which is the same species as the black squirrel, with the black squirrels being a color morph of the gray squirrel.