Hitting the stage in fittingly bright and colorful ensembles, Siwa and her pro partner, Jenna Johnson, delivered an energetic and exciting Quickstep set to "Are You Gonna Be My Girl" by Jet. The pair -- who are the show's first-ever same-sex dance couple -- earned a total of 29 out of 40 for their routine and ended the night on the top of the leaderboard.
Siwa and Johnson spoke with ET's Lauren Zima backstage after the premiere and the young star opened up about how it felt to earn the night's best score.
"It was so cool! I didn't know when it happened!" Siwa recalled. "When Tyra said it was the highest score of the night, I lost it."
The judges had nothing but praise for their routine, and while feedback was rushed to accommodate Monday night's live show, it's clear that even with a small slip-up and the routine loosing some control in the middle, the judges felt that this was the best dance of the night.
And their scores reflected just that. Carrie Ann Inaba gave them an 8, while Bruno Tonioli, Len Goodman and Derek Hough handed out 7s, for a total of 29 out of 40 -- placing the pair firmly at the front of the pack.
As this is the show's first same-sex pairing, Johnson admitted that there was a bit of a learning curve at first, but one they both overcame quickly.
"It was definitely new territory for me, but the second I met JoJo I felt like this was meant to be," Johnson told ET. "The whole process has been so natural so smooth, and now I'm like, 'Do I even remember how to dance with a guy? That's so last year.'"
During their performance, the two got some enthusiastic support from Siwa's girlfriend, Kylie Prew, who was cheering loudly and excitedly from the audience -- and it seemed to really help.
"Ky is literally the best human being in the world," Siwa marveled with a smile. "Having Kai scream for me here just made my heart so happy."
Siwa and Johnson's major moment also earned them a high score and a lot of love from fans too, many of whom were overcome with emotion over the Dance Moms alum'smonumental DWTS debut.
"@itsjojosiwa I CRIED! Today was historic! NEW FAN! I'm 50.," one user wrote.
"I have a lot of mirrorballs on me. I have a lot of little teensy ones every which way. I am manifesting it," Siwa said. "That's what I've been saying all day today."
"[I'm] very driven and also very competitive," she continued. "I obviously want to win. It's in my blood. I love to win but already doing what I did with this show and with this experience and dancing with another female and being the first, I've already won in a way and of course not the mirrorball yet -- hopefully, manifesting -- but everything that's happened so far and the reaction we've already received from the world is just amazing."
Check out more of Siwa's dance moves when Dancing With the Stars airs Monday nights at 8:00 p.m. ET on ABC.