If you didn't watch the game and heard that Butler got flagged for that, you'd probably assume he got into a scuffle or pushed another players, but that's not what happened at all. The Cowboys were penalized 15 yards on the play because Butler violated a little-known substitution rule.
When an offensive player enters the huddle, he has to participate in a play or else it's a penalty. During the Cowboys' second offensive series against the Packers, Butler  was flagged for doing what you see below.
The penalty was a devastating one for the Cowboys because it nullified a 22-yard gain by Terrance Williams. Instead of getting the ball on the Packers' 15-yard line, the Cowboys had to run their next play from their own 48.
Following the game, Butler was less than thrilled with the penalty, and the refs in general.
"Never heard of it in my life," Butler said, via the Dallas Morning News. "[We] couldn't beat the stripes. You can quote me on that."
A lot of Cowboys fans actually feel the same way as Butler. After the game, many Cowboys fans took to Twitter to point out all the bad no-calls that went in favor of the Packers.
On a different play, the refs said that Jason Witten got his feet tangled with a Green Bay player even though that didn't appear to be the case.
Cowboys fans would probably just have no officials on the field if they ever face the Packers in the playoffs ever again. Besides this game, you also had the "Dez caught it" game after the 2014 season that was won by the Packers after officials overruled a Dez Bryant catch.
As for the crazy penalty on Butler, referee Tony Corrente was asked about that following the game.
"They brought in a two-receiver set on a substitution, and [Butler] was one of those two players and came into the huddle, stayed in the huddle, then departed," Corrente said in his pool report. "He was substituted for. He has to stay either in the game or they can call a timeout and get out of it. Of course, he went out. It's not an obscure rule, it's just part of the substitution mechanics and part of the substitution rule."
Cowboys fans probably aren't going to buy the explanation.