Lady Gaga has one mode: all-in. That’s the lesson Little Monsters learned (again) over the weekend when Mother Monster jumped in the car with Zane Lowe for a surprise A Carpool Karaoke Christmas special — which also starred Dua Lipa and Chappell Roan — and talked about the time she was told to call it a day as a music video extra.

While Gaga treated a surprised Lowe to the spicy lyrics to her 2008 single “Christmas Tree,” she also shared a clip of her late grandmother singing AC/DC’s “Highway to Hell” in tribute to the loud one , her grandma’s proud love of music. Gaga and Lowe were both thrilled when they saw the footage of Gaga’s grandma shouting the lyrics from a living room chair as Gaga urged her, “Get it, grandma!”

After the singer became emotional while talking about the lessons she learned from her grandma, Lowe got out of the SUV to get her a special Christmas present. That gift was, of course, AC/DC singer Brian Johnson. The pair then performed a duet on “Highway to Hell,” with Johnson impressed by Gaga’s powerful pipes.

After some rocking out, Gaga remembered that she was an extra in a 2000 AC/DC music video. “Do you want to hear something funny? “I was in the ‘Stiff Upper Lip’ video,” Gaga told an incredulous Johnson. “I was 17 and was an extra in the back.”

The best part? Gaga said she was headbanging, as one does when listening to AC/DC, before being told to stop. “I was headbanging and they said ‘hmmm.’ No headbanging, we want it to be modern. And I thought, ‘No, there’s only one thing I can do.'”

The segment ended with car fanatic and weekend racer Johnson joking, “I don’t have a driver’s license!” You can watch the full episode now on Apple TV+.

Check out a fan screenshot of Gaga’s “Stiff Upper Lip” cameo below.