The Packers forced a safety late against the Lions. Trailing by two scores, the Lions wanted the ball back, and sent punter Sam Martin to try the rare onside punt. And it worked!
It seems an onside punt is actually a bit easier to execute than an onside kick -- on a drop kick, you can pop the ball up as high as you want, which gives your players more than enough time to gather under the ball, and you don't have to bank on the random bounces of an oblong ball. Randall Cobb called for a fair catch, but nobody got under it in time.
The Lions were still down a lot late, but props to them for pulling this off.