NEW YORK -- Watch out when you invite internet stars to perform -- they might upstage you.

A teen Instagram dancing sensation has gone from online to on-air after Katy Perry invited him to show off his moves during her "Saturday Night Live" performance this weekend.

Fifteen-year-old Russell Horning took the "SNL" stage during Perry's performance of her new single "Swish Swish." He wore his trademark backpack and did his signature move of quickly swaying his hands around his waist.

The "backpack kid" became a hit on Twitter.

The Lawrenceville, Georgia, teen tells USA Today the collaboration came about after Perry noticed him on Instagram.

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But it looks like Horning wasn't too impressed with Perry's dancing. His caption on a video of her trying to imitate his moves backstage at "SNL" read: "When your mom tries to look cool."