Taking the classic stop-time riff from Willie Dixon's "Hoochie Coochie Man," Muddy Waters turns in his own classic, a fully realized refinement of the earlier song, distilled to some pop-worthy hooks like the monstrous riff and the spelled-out "M-A, child - N." The song takes the braggadocio of the former song to new, more confident heights. On the original 1955 recording featuring the legendary Chess Records lineup of Little Walter Jacobs on harp, Jimmy Rogers on guitar, Elgin Evans on drums, Otis Spann on piano, Big Crawford on bass, and Waters on vocals and a slide guitar, Waters testifies to his masculine power, spurred on by whoops and hollers in the background, like a congregation calling out "amens!"
Bo Diddley had taken the stomp riff from "Hoochie Coochie Man" for his own 1955 song "I'm a Man," which Waters answered in kind with "Mannish Boy." Waters is a powerful, swaggering presence at the top of his game here: "Now when I was a young boy, at the age of five/My mother said I was, gonna be the greatest man alive/But now I'm a man, way past 21/Want you to believe me baby/I had lots of fun/I'm a man." He turns some of the lyrics from "Hoochie Coochie Man" on their head, so that the Hoodooo item "John the conqueror root" becomes the thing that everyone thought they heard the first time, "Johnny Conkeroo." "The line I shoot will never miss/When I make love to a woman/She can't resist/I think I go down/To old Kansas Stew/I'm gonna bring back my second cousin/That little Johnny Conkeroo."
The song is a standard, with all the heavyweights covering it, from Jimi Hendrix's acid blues version, to the Rolling Stones' faithful and ebullient cover on Love You Live (1977). Waters himself recorded the song again in 1977 with Johnny Winter for Hard Again. It is an excellent recording with some top-notch sidemen who offer a very spirited performance. James Cotton wails on the harmonica, filling up the mix with his riff.