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David Letterman, is that you? Check out former 'Late Show' host's shaggy beard

The beard may have gotten its start at the Indianapolis 500 in May, just weeks after Letterman's "Late Show" tenure ended.
/ Source: TODAY

If there's a Top 10 list for shaggy beards, David Letterman's might be No. 1.

The former "Late Show" host was spotted sporting untamed facial hair Sunday while walking with his 11-year-old son, Harry, on the streets of New York City.

Letterman takes his son Harry out for dinner in NYC.SEPT 27TH 2015Splash News

About a month after wrapping his 33-year stint as a late-night host on NBC and CBS, the auto-racing fanatic attended the Indianapolis 500, where the 68-year-old was seen wearing a few whiskers that may have grown into Sunday's big beard.

INDIANAPOLIS, IN - MAY 24: David Letterman attends the Indy 500 on May 23, 2015 in Indianapolis, Indiana. (Photo by Michael Hickey/Getty Images)Getty Images file

Letterman's "Late Show" successor, "The Colbert Report" host Stephen Colbert, shaved his "Colbeard" in a YouTube video posted in June, about three months before his CBS debut.

RELATED: David Letterman's final 'Late Show' brings emotional goodbyes, surprise guests

It's unclear if Letterman's new beard will co-star in his next project: the second season of "Years of Living Dangerously," whose celebrity guests investigate the effects of climate change. The Emmy Award-winning docuseries shifts from Showtime to National Geographic for Season 2, and, according to Variety, will feature appearances by Letterman, Jack Black, Olivia Munn and "Saturday Night Live" star Cecily Strong, among others.

Follow writer Chris Serico on Twitter.