Celebrating the release of Mario Party 9, Mario and Luigi showed up to some special parties.
http://www.nintendoworldreport.com/news/29789
Mario and Luigi visited the parties at homes of select winners in celebration of the release of Mario Party 9.
Beginning as a Twitter Question using the hashtag #1UPMyParty, Nintendo asked “Why should Mario and Luigi crash your party?” Nintendo then selected several winners who got a visit from Mario and Luigi. Not only were they visited by the Nintendo icons, but each winner received a special prize package.
Nintendo supplied us with a video that highlights all of the "party crashes." Check out the video below.