Selena Gomez reacted to Billie Eilish's "Bad Guy" being inspired by the Wizards of Waverly Place theme song.

In December, the 18-year-old pop star and her producer-brother Finneas told Rolling Stone the Disney Channel track was the inspiration behind her hit song — and after listening to both, the similarities were uncanny.

As most fans know, Gomez portrayed Alex Russo on the series from 2007 to 2012 and sang the Wizards theme song. So, when she appeared on The Tonight Show Monday night (January 13), host Jimmy Fallon broke the news to her.

"I don't know if you know these, but you have something in common with Billie," he said. "You're an inspiration for the song 'Bad Guy.'"

"Am I the bad guy?" Gomez joked.

Fallon then played both tracks to show the 27-year-old singer and the audience just how similar they are, first playing the Wizards theme song, which Gomez was a little embarrassed to hear. She covered her face at the sound of her young voice. However, she agreed that the tunes did sound very much alike.

"I love Billie," Gomez gushed. "That's so cool, that's so cool."

You can watch Gomez's reaction in the video, below:

Coincidentally, Finneas recently teamed up with Gomez to produce her song "Lose You to Love Me," off her newly-released Rare album, and she discussed what it was like to work with him during her Tonight Show interview.

"We finished up the song and gave it to him to produce himself and he did an amazing job," she explained. "He's obviously extremely talented."

Rare is out now.

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