... is grow a beard!
David Letterman was spotted Thursday walking the streets of New York City with his new retirement sidekick ... a scruffy beard.
It's the first time we've seen the 68-year-old ex-talk show host since he ended his 33 year run on TV.
It's pretty funny ... Letterman is sporting a beard while his replacement, Stephen Colbert, made his first official "The Late Show with Stephen Colbert" video all about ... shaving his beard off.
The free time, and the facial hair, looks good on Dave.