But they didn't arrive together. All four reality TV judges—don't forget Simon Cowell and L.A. Reid!—rolled up to the venue solo.
Read on for all the scoop on Spears and Lovato's X Factor judging debuts...
Over 100 fans lined up outside the Frank Erwin Center behind barricades to get a glimpse of the four walking into the auditorium.
L.A. Reid—in his signature suit and tie—was the first to arrive. He posed for photos and spoke briefly to a house crew, saying, "I love Austin."
Spears showed up with fiancé Jason Trawick looking beautiful and bright in a neon pink Brian Lichtenberg mini dress and YSL pumps. The 30-year-old pop star signed autographs and greeted media members with a simple, "Hello!"
Lovato, 19, arrived next in a yellow Topshop dress and cropped black jacket. She looked at press and smiled, "You're much nicer than they are in L.A."
Both Spears and Lovato have taken to Twitter to share their X Factor excitement. "So excited to be going to Austin this week for @TheXFactorUSA auditions!" Spears tweeted. "Will I see any of y'all there on Thurs or Fri?"
"I'm so excited for the auditions today!!!!" Lovato wrote. "It's my first day... woo hoo!! Who's coming??!!! #XFACTORUSA."
Last to arrive was X Factor head honcho himself, Mr. Cowell, dressed in his usual T-shirt and jeans. When photographers tried to get him to take his sunglasses off for pics, he said, "It's too bright."
About 200 aspiring singers will face the judges during four three-hour show tapings over the next two days (7,000 wannabe contestants were auditioned and screened here a couple of weeks ago).
Now we want to hear from you. How do you think Spears and Lovato will do as X Factor judges? Sound off below!