David Letterman retired from hosting The Late Show last May, and a few months afterwards he started sporting a beard. But here's the funny thing about beards—they just keep growing if you don't trim them. It turns out that's exactly what Letterman has done during his retirement, along with staying fit and vacationing in a tropical place. Pretty standard retirement stuff.

Pictures of Letterman's new look, including a shaggy beard, shaved head, and jogging gear, went viral on the Internet on Wednesday. Fans were just a bit surprised to see the contrast from the clean-shaven, bespectacled Letterman they remember from TV. Here are some of their best reactions:

Sources: Twitter