Here's a better angle of the play:

A Redditor explains:

Because everyone views him as "fragile" it helped Peyton Manning a lot. A normal quarterback would try something like this, but nobody thinks a man who is almost 40 and has had several surgeries would try and carry the ball himself. The team also put on a good show. 

As a Bronco fan, I laughed my ass off for a good few minutes after this.

The Cowboys really showed up though. Final score was 51-48. In fact, if it hadn't been for a key interception, the Cowboys probably would have won. It was the first game all season that made Bronco fans look straight into the eyes of defeat.

Peyton Manning has the turning radius of a battleship.

From twitter Denver Broncos Verified account ‏@DenverBroncos:

Manning said he was the only one that knew he'd keep the ball on his TD run so that everyone else would sell the RB run better.

So wait, Peyton Manning didn't tell ANYONE what he was going to do?!

Also:

Manning's rushing stat line this season? 12 carries, -15 yds, 1 TD. His 1-yd TD run was his 1st run for more than 0 yds this season.

Also:

Peyton Manning's projected 2013 stat totals: 480-634 for 6,029 yds, 64 TDs, 3 INT. All but attempts would set @NFL records.