A Vine star is competing on 'Dancing With the Stars' and the hosts can't get over how old he is

"Dancing With the Stars" welcomed its youngest male cast member to date this week: Vine star Hayes Grier.

Hayes, 15, is one of a group of young male Vine heartthrobs with millions of followers who travel the country making live appearances. On DWTS, he has been paired with professional dancer Emma Slater, 26.

Hayes has over 4 million followers on Vine and has been using the platform along with his brother, Nash Grier, for about two years. You might remember Nash from the backlash he met when he was caught screaming a homophobic slur on Vine in 2014. Nash is still the second most-popular person on Vine.

When an LA news crew asked Hayes what he's known for on Vine recently, he said, "I would dance really weird."

Here's a recent example:

Most of his recent Vines, though, are promotional. He Vines about upcoming appearances and re-posts clips his fans have made devoted to him.

Predictably, his teenage fans have been losing it ever since he announced he'd be joining the cast on Aug. 27.

They're posting under the hashtag #HayesDWTS and imploring other users to "vote for Slayes," Slater and Hayes, since DWTS is a voting-based show.

—hailey_marie_grier (@CuretonHailey) September 15, 2015

—bruhitzfaith (@JackJandJackgF) September 15, 2015

—adrianna/PLS HAYES (@hayesftbiebs) September 15, 2015

They also freaked out when his brother, Nash, appeared in a shot wearing a shirt that said "Hayes Grier's Brother."

—adrianna (@CHARGEDUPDALLAS) September 15, 2015

Cast members on "Dancing With the Stars," though, are more fixated on his youth than his Vine stardom.

On Monday night, when the latest season of "DWTS" premiered, Hayes and Slater were shown rehearsing a dance to "Cheerleader."

"I didn't think the difference between 26 and 15 was noticeable," Slater mused, "but it is."

Hayes also had some thoughts about Slater's age.

"She doesn't look 26, if that makes her feel any better," he said in a confessional.

The judges, too, were agog over Hayes' youth — not necessarily in a good way. Carrie-Ann Inaba remarked that he still had "youthful gawkiness," but charitably added that he "still has a little room to grow."

They ended up scoring 21 out of 30 from the judges. Not too shabby.

Here's Hayes' dance: