David Letterman's "Stupid Human Tricks" is back with a chewy vengeance.

In more proof that you can never really figure out or understand just why something gores viral, this old clip of a teenage girl performing on Letterman's popular "Stupid Human Tricks" is trending.

The trick is, well, stupid, although it probably makes her a hit at parties, even all these years later. The girl manages to spit out a piece of gum and then suck it right back in. It's a pretty weird talent -- almost as weird as why it's making the rounds online again now.

Maybe this will open the flood gates for some other great Letterman bits of yesteryear -- it's been far too long since we talked about Drew Barrymore flashing him on his desk, right?