Portland versus Seattle. It's one of the most anticipated match-ups of each MLS season. But it's not just the teams, the players, and what happens on the field that makes this rivalry so special -- the fans play a huge role, too. From taunting tifos to screaming supporters' groups, the pageantry put on by fans is just as responsible as the on-field theatrics for making any Timbers-Sounders game special.Get to know the fans that make this rivalry a marquee event, how they came to support their respective teams and what they think about their Pacific Northwest neighbors.Don't miss Seattle-Portland this Sunday at Providence Park (10 pm ET | ESPN2 in the US, MLS LIVE in Canada).