Michael Jackson says "shamone" (or "cha'mone" or c'mon), which probably means "come on". You can hear him saying this in some of his songs, like "Bad".
The word or expression "shamone" (or "cha'mone") is one of the most recognizable vocal hallmarks of the musician Michael Jackson. Described as a "ridiculous, funky, fantastic invention" , the oft-repeated deliberate mispronunciation is found in many Jackson songs, with the original lyric most likely being "c'mon" (which is how it appears in the "Bad" lyric sheet), or possibly "jam on". Its ubiquity in Jackson's work led to it becoming something of a joke among fans soon after its first usage, but it has recently gained mass popularity as a catchphrase, with a minor appearance in Rush Hour 2 as Chris Tucker sings "Don't Stop 'Til You Get Enough", and more extensive use in the British Channel 4 comedy sketch show Bo' Selecta! with a caricature of Michael Jackson played by Leigh Francis. The Bo' Selecta website and merchandising always use the "cha'mone" spelling. South Park's "The Jeffersons" episode makes extensive use of "shamone" and several other of Michael Jackson's unique and immortalized sounds, though they later revealed that they got the idea from Bo' Selecta!.
The expression is also used twice (glossed as "show more" and "sh-mowa" in the DVD subtitles) in the cult BBC comedy hit The Office; once by Tim while performing a Michael Jackson impression, and later by David Brent as the coda to his rendition of Pink's "Get The Party Started". The latter embellishment was originally improvised by Ricky Gervais as a successful attempt to cause actor Martin Freeman to "corpse" (i.e. ruin the take by laughing).
In popular usage, the word largely functions as an interjection. It is often used in the TV series Bo' Selecta! (and has thereby entered the vernacular in the UK) in conjunction with an expletive, such as "Cha'mone, ************!"; or as a salutation such as "Shamone, brothers!"; or as an expletive in its own right, as in "I'm gonna get you, shamone!". Bo' Selecta! also makes use of Michael Jackson's 'hee hee' which is most prominent in Another Part of Me.
Other oft-noted (and impersonated) vocal tics and mannerisms include James Brown's rhythmical screams and grunts, and Mark E. Smith's trademark cadent "ah"s.
The best known use of "cha'mone" is in the first line of the chorus of Michael Jackson's "Bad": "I'm bad! I'm bad! Cha'mone!" It also features prominently in a number of recent songs including "Rockin' The Suburbs" by Ben Folds, and "Fever" by Pink Grease.
New York based pop band the Scissor Sisters used the word in their hit single "Laura".
Another place the word "cha'mone" can be found is at about :35 seconds into the song "Keep On Truckin'" by Eddie Kendricks. Although in reality it just sounds like "cha'mone", he's actually singing "shame on me".