By now, everyone knows T-Mobile US (TMUS) CEO John Legere is an extraordinarily mischievous manager. But he took the hijinks to new heights on Monday night.

Legere showed up at rival AT&T’s (T) party concert at CES in Las Vegas, where he ran into CNET reporter Roger Cheng. Cheng promptly posted a picture of the T-Mobile exec on Twitter.

Ran into @JohnLegere at the AT&T party. Yep, he crashed it. And still wearing the pink t-mo shirt. #CES2014 pic.twitter.com/gy9vGTJUEW — Roger Cheng (@RogerWCheng) January 7, 2014



A pretty hilarious marketing stunt, though not for AT&T, which promptly dispatched security to throw Legere out, prompting another tweet from Cheng.



Oh wow, security just escorted @JohnLegere out of the party. AT&T is not happy with my tweet. #ces2014 — Roger Cheng (@RogerWCheng) January 7, 2014



That lit up the Twittersphere – and garnered another gazillion dollars worth of free publicity for Legere and T-Mobile.









Oh no he didn't ! "@BuzzFeed: T-Mobile’s CEO @JohnLegere Crashed An AT&T Party In Vegas And Was Thrown Out http://t.co/jHsSJrdKw2" — ✨Christine❤ (@CPookie) January 7, 2014

Congrats @ATT for playing Goliath to @JohnLegere 's T-Mobile David... You gave them earned media. I foresee Good things for the #uncarrier ! — G Scott Stukey (@gscottstukey) January 7, 2014





Hahaha @ATT some punks. The fact that @JohnLegere has the balls to let AT&T know what's up in person says a lot. Respect! 👍👏 — Audi *KCCO* (@iAudi3) January 7, 2014





Legere said he was just trying to get into see featured music act Macklemore.

But AT&T had good reason to take offense at Legere's party crashing. Since taking the top job at T-Mobile in September, 2012, Legere has made AT&T his top target for competitive attacks and sometimes off-color quips. Just last week, AT&T hit back, offering up to $450 to new customers switching from T-Mobile.



Legere was hired after T-Mobile's prior CEO Philipp Humm's failed effort to sell the U.S. unit to AT&T for $39 billion. In the aftermath, AT&T had to fork over $3 billion and access to some spectrum rights.



Since coming on the scene, Legere has tried to turn AT&T into a punching bag. In a July press conference, he took to the stage with a group of dolls to mock AT&T's commercials that feature cute and precocious little kids. "Hey kids, is it better for your network to be crap or is it better to have a good high-speed network in New York?" he asked. At an October global event, he called other carriers' fees "completely crazy" and "insanely inflated."

And the aggressive approach appears to be succeeding. T-Mobile's stock price has doubled since May, when the shares first listed on the New York Stock Exchange. And T-Mobile added almost 1.4 million subscribers to its branded services in the first nine months of 2013, after losing 1.1 million in all of 2012, according to the company’s figures. Many switched from AT&T, according to analysts.

Legere fans won’t have to wait long for his next trick. Legere speaks to Yahoo’s new tech reporter David Pogue later this week. And the CEO has scheduled a press conference for Wednesday to unveil the fourth piece of his “Uncarrier” strategy. So far, he’s ended two-year contracts, slashed prices for monthly contracts and global roaming and separated the cost of phones from service fees.

What’s next for the T-Mobile trickster who calls batman a role model? Rumor has it he may attack family plans next. AT&T and Verizon Wireless (VZ) offer family plans that bundle multiple accounts onto one bill but don’t save customers much money, if any. Volume discounts could be in order.

Another rumor has it that T-Mobile will offer to cover early terminations fees for new customers switching from another carrier. That prompted AT&T's pre-emptive strike last. Though the #2 carrier said it would pay “up to” $450 to customers switching from T-Mobile, $250 of the potential windfall would be paid for turning in a used phone and the offer didn’t include a subsidized price on a new phone.

Just wait until Legere gets on stage to talk about that one.