Already a regular singing partner with Tony Bennett, Lady Gaga found another golden oldie chart topper to pair with: Mario Andretti.

Gaga was at Indianapolis Motor Speedway for the 100th running of the Indy 500 on Sunday, though she kept a fairly low profile, dressed down in jean shorts with her hair pulled back in a tight ponytail.

Gaga and 1969 Indy 500 winner Andretti rolled onto the track with the field of 33 drivers before Sunday's race in a custom-built, two-seat Indy car. Gaga was a late substitute for country star Keith Urban, who was unable to participate after injuring his back.

Gaga gave team owner Michael Andretti a kiss on the cheek before the start of the race.

"Travel to any corner of the globe and people know exactly who Lady Gaga is," Indianapolis Motor Speedway President Doug Boles said.