Oh snap

[Becky]

(exclamatory phrase) a playful indication of surprise, misfortune, or insult
popularized by Tracy Morgan of Saturday Night Live, OH SNAP is seemingly derivative of [oh no you didnt] where an insulted person, for example a guest of Jerry Springer or often a spunky African American woman contends the insult being made against him/her. While derivative of oh no you di-int, OH SNAP has more of an emphasis on playfulness and can be said by people other than those being insulted.
see also: [OH ZIP]

[Britney]

First known usage was by the 1980s rap song Just a Friend by Biz Markie. Its a rated G way of saying oh shit

[PussyCat]

Commonly Used By [Dave Chappelle], the phrase is an exclamation of surprise, reget, dissapointment, happiness, and many other emotions.

[Donald Trump]

an expression used to convey a feeling of exclamation

[Tanya Shivari]

People usually say Oh SNAP! as an exclaimation, and it can be either positive or negative.