It's tradition in the Winter Classic. Or, at least, it was. At the end of the game, the teams shake hands, just like at the end of a playoff series.
Tonight, the Penguins and the Capitals broke that tradition.
A report on Twitter said that some of the Pens had to be reminded to stick around on the ice for handshakes. That never happened. Mutual decision by both teams? Interesting, either way. I guess they really do hate each other.