18. 'Welcome Back, Kotter'
It was primarily a vehicle for comedian Gabe Kaplan and his Groucho Marxisms, but the show had two major things going for it: John Sebastian's lilting earworm of a theme song, and the Sweathogs, the core group of four ne'er-do-well outer-borough students led by a young, on-his-way-to-superstardom John Travolta as Vinnie Barbarino. Loaded with catch phrases ("Up your nose with a rubber hose!"), the Sweathogs became a pop-culture phenomenon, as well as a welcome representation of inner-city students that you didn't see on TV in those days and the template for all the small-screen freaks and geeks to come.