A.J. McLean got to relive his Backstreet Boys glory days in front of a hard-partying crowd ... all thanks to a '90s cover band.
McLean hit up a '90s Throwback Party at Greystone Manor in West Hollywood Thursday night and when a '90s cover band started playing the BSB hit "Everybody," McLean went nuts.
Check out the video ... A.J. kills it on air guitar.
Backstreet's back ... sorta.
Waiting for your permission to load the comments.