bitter rivalry

Some NHL rivalries evolve from a big game, a major trade or a short-lived scuffle, then fade after a few years.

Not the Philadelphia Flyers vs. the Pittsburgh Penguins. This rivalry is real, perpetual, and, mostly, downright nasty.

Evolving from state lines and bloodlines -- and it's mostly bad blood -- it's been one of the league's most heated since the teams were born in 1967.