Jennifer Lopez may have a rep as demanding, high maintenance and one hell of a diva, but it came in handy at the 2013 Grammys.

With a mere flick of her thumb -- which possesses more power than most of our entire bodies -- J to the L-O got a Grammy crasher to get the H-E-L-L out and prevented him from interrupting Adele's acceptance speech.

Adele was walking onstage to accept her golden gramophone for Best Pop Solo Performance when Ukrainian TV presenter Vitalli Sediuk approached. He told her, "It's such an honor to win this award! I love you Adele!"

He was about to join the confused chanteuse onstage when Lopez warned him with one mere gesture and ferocious glare otherwise, and he exited upstage. (Lopez completely kept her cool, even as she looked over her shoulder to make sure he was gone.)

Sediuk is the same guy who got slapped by Will Smith when he tried to smooch the star at the 'Men in Black 3' premiere -- a repeat offender in terms of celeb harassment disguised as pranks.

Here's where it gets scary: the awards had heightened security because of the Christopher Dorner manhunt and this guy still got in without tickets or any sort of clearance. Sources said he just strolled in alongside Katy Perry, who apparently inadvertently distracted everyone with her rack.

Once he got into the arena, he plopped himself down in the second row behind Justin Timberlake. It turns out Adam Levine was actually supposed to take that seat, but he came late and just sat elsewhere instead of being a pain in the ass about it -- the one time it would have paid off.

Once Sediuk got offstage, he was finally apprehended (and noticed) by Grammys security and arrested, spending the night in jail.

If only they'd do the same with Chris Brown.

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