The "Mitzvah Tantz" (tantz=dance) performed at weddings is a Hasidic custom of the men dancing before the bride on the wedding night during the reception. It is a mitzvah dance because of the commandment to rejoice with the bride and groom on their wedding night. The Hasids must have appropriated the custom because it is mentioned earlier in the medieval Machzor Vitri (compiled by Simhah ben Samuel of Vitry, who died in 1105).
In the Talmud (Tractate Ketubot 16b-17a), the question is raised: keitzad merakdim lifnei hakallah ("how do we dance before the bride?"). While the question in the Talmud focuses on the debate between the schools of Hillel and Shammai as to whether honesty is the best policy in the case of describing an ugly bride to the groom, there should be no question that it is an honor to dance for the bride on her wedding day. Today, at traditional Jewish weddings, the men sing "keitzad merakdim lifnei hakallah" while dancing joyfully in front of the bride.
Those words came to mind the other day while I watched the popular YouTube video of actor Lin-Manuel Miranda entertaining his bride, Vanessa, at their wedding. Miranda, who wrote and scored the Tony Award winning hit "In the Heights," recruited the bride's father and the bridal party to perform the song "To Life" from "Fiddler on the Roof." Neither the bride nor the groom are Jewish, but they managed to have the word "L'chayim" mentioned more at their wedding than at many Jewish weddings. While not a traditional Jewish wedding ritual, this production clearly fits the mandate to dance before the bride.
Interestingly, in recognition of his portrayal of the Washington Heights neighborhood in "In the Heights," Lin-Manuel Miranda received an honorary doctorate from Yeshiva University, which is located in that neighborhood. The actor, who also appeared in the TV show "House," is the youngest recipient of an honorary doctorate from YU.
I think it's fair to say that Lin-Manuel Miranda answered the question: keitzad merakdim lifnei hakallah. Mazel Tov to the bride and groom! Here's the video: