'Dancing With the Stars': Backstreet Boys Member AJ McLean Making Surprise Appearance

There's going to be some serious throwbacks on Monday's episode of Dancing With The Stars as the show will feature its "Boy Bands and Girl Groups" theme. That means viewers can expect plenty of music from the likes of *NSYNC, Spice Girls and New Kids on the Block.

Oh, and the Backstreet Boys, who will also have a special guest appear on the show. In a sneak peak exclusive to E!, Lauren Alaina is in for a surprise as her and her partner, Gleb Savchenko, prepare to take on one of the band's iconic songs, "I Want It That Way."

One of the band members, A.J. McLean, surprises the two as their practicing their routine. Alaina and McLean are actual friends in real life after meeting each other at 2018 CMT Awards.

In the clip, McLean calls the country singer, "the most talented person in quite some time."

"She's dominated the singing part, and now she's dominating with her feet. I wish you the best of luck, babe. You're gonna kill it," McLean tells Alaina.

After taking in some pointers from McLean, Alaina shares that she's ready to nail this performance. As she puts it, "I cannot let the Backstreet Boys down."

Heading into Week 9, Alaina finds herself among the highest scorers in the competition despite a slip-up in Week 8 that saw her net a 24 out of 30 while two other performances garnered perfect scores. The week prior, Alaina was atop the charts with a combined 54 out of 60, which tied with two others.

It's also worth nothing that Alaina has been doing all of this with broken ribs. She admitted after one of her recent performances that she suffered the injury early on in the competition and kept it a secret.

She shared a post on Instagram explaining how challenging the competition has been and even more so with the injury.

"It has tested me mentally, spiritually, and physically," she wrote. "I am so proud of how far I have come in this time. I am going to leave this experience a much better woman than when I started. Thank you, Gleb, for your patience, hard work, and belief in me. God put me exactly where He wanted me. I am so thankful for the love, support, and votes you guys have given us."

Dancing With the Stars will air on ABC at 8 p.m. ET.