The preseason got off to a hot start for Panthers linebacker A.J. Klein on Thursday when he picked off a pass in the first quarter against the Ravens and returned it 95 yards for a touchdown.

Unfortunately for Klein though, the touchdown didn't count, thanks to a crazy, and rarely called penalty, that Cam Newton was flagged for during the return.

During Klein's return, Newton ran onto the field before the linebacker reached the end zone, which means the Panthers had 12 players on the field. The officials noticed Newton and immediately flagged Carolina for an "illegal substitution."

The touchdown was then taken off the board and the Panthers got the ball at Baltimore's 26-yard line.

As you can see below, Newton was in shock when he found out that he had been penalized.

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Cam Newton seemed slightly shocked about being penalized against the Ravens. NFL.com screengrab

Newton even tried to plead with the officiating crew to overturn the call.

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Cam Newton was not happy with the officiating crew on Thursday. NFL.com screengrab

Although officials don't usually throw a flag in this situation, that's going to change in 2016. Each officiating crew has been told that players and coaches leaving the sideline is a point of emphasis this season, and that a flag should be thrown if it happens.

After the game, Newton had a pretty simple explanation for why he ran on the field while a play was still going on.

"I just got too excited," Newton said, via ESPN. "I was hoping they would give a warning."

During his postgame press conference, Newton refused to answer when he was asked if he said anything to Klein or offered an apology.

"Next question," Newton said. "I don't want to have a discussion about something that I've learned from. You live and you learn ... It happened. We all learned something as a team. We're moving forward."

For the record, Klein says that Newton did offer an apology.

"He came up and apologized, that could've possibly made the difference in the game," Klein said after the loss. "It's just learning a lesson for the regular season. Everybody's got to be on their game."

The good news for Newton is that the penalty didn't end up hurting Carolina that much because the Panthers ended up scoring on the drive.

The upside of Newton's penalty is that the Panthers defense was thrilled to see their starting quarterback so emotionally invested in a preseason game.

"I was like, 'This is really special. You guys really threw the flag on him?' I want to see it on film. I want to see how far he was on this field," Panthers safety Kurt Coleman said, via the Charlotte Observer. "But you know what the great thing is? He's actually engaged in the game. He was excited for the defense. He got the flag, but he's actually in the game. That shows a lot about himself."

Anyway, since this is the preseason, there's a good chance that everyone will forget about this and move on by the time you're done reading this.