Psy, MC Hammer Gangnam Style YouTube video: How the American Music Awards mash-up came to be

Watch video below:

We should've known something was up when Psy took the stage at the "American Music Awards" in a pair of Hammer pants.

The "Gangnam Style" artist had the AMAs audience on their feet doing his trademark dance when the lights suddenly dimmed and MC Hammer appeared on stage - still "Too Legit to Quit."

Younger viewers might've been a little lost when Psy stopped and went Hammer-time, as the "Too Legit" single came out just over 20 years ago. But, as the YouTube clip above proves, Hammer hasn't lost his touch.

Backstage, Hammer told CNN that the performance came together with the aid of Justin Bieber's manager, Scooter Braun.

"Scooter Braun connected us, and [when] I spoke with Psy I knew right away that he is a good guy. I like working with good people ... I loved doing it and we had a great time together," Hammer said.

"Psy is fantastic. He's shifted the planet. He's got the whole world dancing. And it's a rarity in this world. Only four people made that happen in history - James Brown, Michael Jackson, yours truly and Psy. "

Psy, who even convinced Hammer into pulling on his trademark pants once again, didn't have any nerves about hitting the old-school routine.

"Honestly, I practiced his move[s] 20 years ago," Psy said. "So I've done that for 20 years."