Almost as famous as the opening four notes from TV's Dragnet, the opening four-note riff from Bo Diddley's "I'm a Man" is certainly the most recognizable blues lick in the world. Adapted from the stop-time figure utilized in Muddy Waters' recording of Willie Dixon's "I'm Your Hoochie Coochie Man," Diddley simply dispensed with the regular blues progression and just kept repeating the four-note riff over and over, creating a trance-inducing piece of music and male bragadaccio in the bargain. Because the tune was so simple, it was also easily imitated, spinning off numerous cover versions and tunes based around the same riff. Certainly one of the most spirited covers was by the Yardbirds, complete with double-time rave-up guitar solo courtesy of Jeff Beck, which inspired several other covers of that arrangement alone by various garage bands. Diddley himself would recycle the riff on several follow-ups like "I'm Bad," "500% More Man," "Oh Yeah," and "Shut Up, Woman." Even stranger was Muddy Waters' "Mannish Boy," loosely based on Diddley's tune with added verses, Waters recording the tune in answer to Bo using his riff from "I'm Your Hoochie Coochie Man," art imitating life imitating art. But the original is still the champ, speaking to every macho-infested romantic notion most people have about the blues.