6. Felix Unger and Oscar Madison, 'The Odd Couple'
Ideally, the Odd Couple theme song is playing in your head the entire time you were reading this article. Regardless, it's hard to imagine very many of the entries on this list without first establishing Tony Randall's fastidious Felix Unger and Jack Klugman's slovenly Oscar Madison as the basis for the format. Springing from the equally iconic duo of Jack Lemmon and Walter Matthau in playwright Neil Simon's Broadway original, Randall and Klugman parlayed their clashing sensibilities into comedy gold, giving rise to a phrase used to described mismatched yet utterly perfect pairings to this day.