Taylor Swift has been rocking just about every stage she's hit on her "1989 World Tour." But when she performed the first of two shows in Philadelphia on Friday night (June 12), Taylor brought out a few surprise guest to make evening even more special.

"So what can I do to surprise Philadelphia?" she told the crowd.

Dressed in a crisp white outfit, she then continued the introduction by saying, "Okay so there's this song that came out this past year, and it embodied what we all feel when we feel like [sigh] there's these people who feel so cool that you can't catch up with them. You can't get on their level, and you know they're just like cool kids."

Once she uttered those last words, the crowd erupted into cheers as Echosmith came onstage. Taylor took her place next to the band's frontwoman Sydney Sierota and the group walked down the catwalk as they performed "Cool Kids." And while Noah and Jamie Sierota played their instruments while walking across stage, drummer Graham Sierota used a shaker till he got to his solo drum at the front.

Echosmith were so excited for the opportunity to perform with the "Style" pop star that they shared their thoughts on Instagram, which you can see below.

That wasn't the only treat she had. Taylor also brought out "Bad Blood" stars Justice and Mother Chucker, aka Mariska Hargitay and Cara Delevingne, to say hi to the crowd.

Cara also posted a selfie of the two and expressed how grateful she is for their friendship. "I am so proud to call you my friend @taylorswift what an amazing show! You blew my brains as per usual! Keep inspiring the generations to come x #tillweare100," she captioned the Instagram pic.

Taylor will be playing one more night in Phily tonight (June 13) before heading over to Germany for the European leg of the tour. See all the dates here.

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