Backstreet Boy

Sorta Threatens

AJ and Nick

2/8/2009 3:23 PM PST BY TMZ STAFF
Brian Littrell has seen two Backstreet Boys fall off the wagon recently -- AJ McLean and Nick Carter -- and the guy was serious when he told us they better "clean their act up" if they want to remain Backstreet Boys.

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Thing is, Brian said he and the boys are hitting the studio tomorrow to start a new record... so he -- and his trusty new cast -- can knock some sense into 'em.