'By the way, I'm drunk now': David Letterman makes an appearance at Indy 500 one year after retiring - while Lady Gaga hits the track and Chris Pine is the starter for the 100th race won by a 24-year-old rookie
- The former Late Night host is sponsoring a car in this year's Indy 500 - and said he would fake his own death if he didn't win
- Lady Gaga replaced Keith Urban and rode with driver Mario Andretti for the parade laps before the race
- Star Trek actor Chris Pine waved the green flag to kick off the race at Indianapolis Motor Speedway Sunday
- More than 400,000 spectators were expected at the 100th edition of the race, which began in 1911
David Letterman joked about being drunk during an interview at Indianapolis 500, one year after retiring from hosting his Late Show - while Lady Gaga and Chris Pine both participated in the 100th running of the race.
More than 400,000 spectators were expected at Indianapolis Motor Speedway on Sunday to witness last year's champion Juan Pablo Montoya try to defend his title - but he crashed out of the race at lap 64 while rookie Alexander Rossi rose to the top.
Meanwhile Letterman, 69, co-owns Rahal Letterman Lanigan Racing, the team represented by driver Graham Rahal Sunday.
'If we don't win the 100th running, I have every intention of faking my own death,' Letterman told ESPN ahead of the race Saturday.
'I know a fellow who will remove my fingerprints. I have a post office box somewhere on the planet. That's all I can tell you.'
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David Letterman (pictured at the Indianapolis Motor Speedway Sunday) sponsored a car during this year's race and said he would fake his own death if his driver didn't win
Lady Gaga (left) stepped in to replace country singer Keith Urban and took a ride with 1969 Indy 500 winner Mario Andretti (right) before the race
Letterman shared a story about drinking too much once in the past, saying: 'We got as drunk as you can get without killing yourself from alcohol poisoning.'
He drew cheers from the crowd when he added: 'By the way, I'm drunk now.'
Letterman, who was born on Indianapolis, told the Indy Star on the starting grid Sunday how he filled his days, one year after filming his last episode of Late Show With David Letterman.
'I had a dental appointment yesterday and I picked up some dry-cleaning this morning,' Letterman said.
He told the newspaper he would donate memorabilia from his career in television to his alma mater, Ball State University in Muncie, Indiana, but admitted it was 'mostly junk'.
Star Trek actor Chris Pine (pictured) also got involved on Sunday as he waved the green flag signaling the start of the race at Indianapolis Motor Speedway
Andretti (pictured with Gaga on Sunday) said the singer would distract him 'quite a bit' and that he hoped he would be able to look ahead whole driving with her in the car
'The poor folks at Ball State are going to end up with a load of my old crap,' Letterman added.
Meanwhile, Lady Gaga stepped in at the last minute on Sunday to replace country singer Keith Urban, who couldn't come due to a back injury.
Gaga rode with 1969 Indy 500 winner Mario Andretti for three parade laps before the race.
'She's going to distract me quite a bit, actually,' Andretti told the Indy-Star before taking Gaga on the ride. 'I hope I can just look ahead while I'm driving.'
The singer held Andretti's hand and gave him a kiss on the cheek before the race began.
She spent more time at the racing track, looking relaxed in shorts and a t-shirt, with her hair tied in a ponytail.
Star Trek actor Chris Pine also got involved on Sunday as he waved the green flag signaling the start of the race.
He was seen in a black t-shirt and pants Sunday, shielding himself from the Indiana sun with a hat and sunglasses as he accomplished his honorary starter duties.
The first Indianapolis 500 took place on May 30, 1911 - and was cancelled several times during the two world wars.
Rossi, a 24-year-old American driver, won the 100th running Sunday right as he ran out of fuel.
He had so little left, the Indy Star wrote, that he couldn't drive it back to the finish line to celebrate his victory.
'I have no idea how we pulled that off,' he said. 'We struggled a little in the pit stops... I can't believe that we've done this.'
Drivers are considered rookies at Indy 500 when they have never qualified for the race and have never started it, according to the Chicago Tribune.
Sunday marked the first time a rookie won the competition since 2001.
Gaga (pictured during the National Anthem before the race on Sunday) attended the race instead of Urban, who couldn't make it due to a back injury
Sunday's race (pictured) marked the 100th running of the Indianapolis 500, which began in 1911 and was cancelled several times during the two world wars. American driver Alexander Rossi, 24, came first
Rossi (pictured celebrating on Sunday by drinking a bottle of milk as per Indy 500's tradition) is the first rookie to win the competition since 2001
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