General Nathan was an American army general who appeared in the episode Get Schwifty as the secondary main antagonist. He wanted to destroy the Cromulons with nuclear weapons, but the President disagreed. He attempted a coup against the President and knocked him out in order to launch nuclear weapons at the Cromulons, only for his plan to destroy them to fail. He is zapped by Rick's particle beam wristwatch when he attempts to murder the President, and therefore turned into a snake.
General Nathan's overall appearance, way of speaking and manner is likely a reference to Gen. Buck Turgidson, a similar military character played by George C. Scott in the movie "Dr. Strangelove."