The show revolves around C.I.A. Agent Stan Smith, and his not so average family. Stan is constantly fighting off terrorists who threaten the safety of the United States, sometimes causing more harm than good.
His wife Francine is your average house wife. She juggles Stan and the kids while keeping a sound mind. Hayley, Stan's only daughter, is your average rebellious teenager. She speaks her own mind, and does things her own way.
Steve, Stan's only son, is a bit of a "geek". He enjoys games like Dungeons and Dragons, and participating in comic book conventions. Although he's not Stan's dream son, he always makes him proud.
Then there's Roger, the illegal alien (literally) who the Smith's are keeping protected. Roger deals with your average alien emotions, and the fact that he is not allowed out in public, which causes him great distress.
Last but not least, Klaus, the Smith's wisecracking talking fish (well, after he was removed from his body) who is secretly in love with Francine.
American Dad! - The Census of the Lambs Synopsis and Schedule