What would cause Sam to threaten Dean with a drive-by?

What would make Dean so concerned when he looked in the backseat of his brother's car?

Based on the official promo for Friday's "Two and a Half Men," we think we know the answer. But watch this sneak peek and take your best guess:

[video url="http://www.tvfanatic.com/videos/whats-in-the-backseat/" title="What's in the Backseat?"] [/video]

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.