In Pilot, when the guys found out that Jess was dumped by her new date (just because she text messaged the guy seven times before the date) they hurriedly rush to the restaurant where Jess miserably waited. As soon as the boys arrived they sang Dirty Dancing'sTime of My Life to motivate Jess back again to the point where the restaurant manager scolded them and told them to go away.
Nick and Schmidt stood up for Jess when Spencer refused to hand her shirt back. Winston thought the idea was ridiculous but after Jess said that she loves her new roommates, including Winston whom she just met that day, and happy with it; Winston joined the rest of the boys and stood up for Jess to get her shirt back.
Slow motion chicken dance. Nick 'finally' gets over Caroline and he shows that he accepts Jess for who she is — a strange girl who dances the chicken dance differently. Schmidt and Winston joining in made it even better. Doubles as a Crowning Moment of Awesome, too.
Instead of going to the airport to catch his flight to spend Christmas with his family, Nick drives a heartbroken Jess, fresh from her break up with Paul, to the street with all the fantastic Christmas lights (which she hadn't gotten to see turned on during the day) to cheer her up. When they get there, however, it's so late that everyone has turned them off for the night. Not being discouraged, Nick starts banging on peoples doors shouting "Turn on the lights". Jess, Schmitt, Winston, Cece and finally Jess join in, running up and down the street shouting for everyone to turn on their lights until the street magically lights up and Jess gets to see the decorations.
Everything Jess does for Nick at his father's funeral. From sobering him up to dressing up as an Elvis impersonator (It Makes Sense in Context) to facing his mom.