The guys from the Backstreet Boys and New Kids on the Block hosted parties at Gallery Nightclub and Chateau Nightclub respectively last night -- after they played the Mandalay Bay Events Center.



What year is it again?

It's official ... Twitter saves lives -- in fact, Donnie Wahlberg from New Kids on the Block was able to help find a NEW KIDNEY for an extremely sick fan ... using nothing but the social networking site.



It all started with a tweet from the fan's best friend who was trying to raise awareness about the girl's dire situation -- one of her kidneys was failing ... fast.

Donnie retweeted the link to his 183,000 followers, asking for help ... prompting a barrage of phone calls to Vanderbilt University Medical Center where the girl -- named Bobbette Miller -- was being treated.

According to the Boston Herald, the calls yielded SIX matches -- and Bobbette is now scheduled for a transplant in June.

Ah, the power of 140 characters or less.

Boy bands of yore New Kids on the Block and Backstreet Boys are joining forces to pay their bills go on tour together.



Question is ...

DJ Pauly D thinks he's got the right stuff for the upcoming New Kids on the Block/Backstreet Boys tour -- and now TMZ has learned he's "in talks" to be one of the opening acts.



Sources tell TMZ .... the "Jersey Shore" star is close to a deal -- but he's not the only act that's being considered. We're told Boys II Men is also in the running. 

Reps for the tour tell us, "[Pauly D] is one of many that has submitted himself to be on the tour. No opening act decisions are being made at this time."