Watch John Mayer Cover Beyonce's 'XO' at 'Boy Meets World' Star Danielle Fishel's Wedding

John Mayer
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John Mayer attends The 57th Annual Grammy Awards at the STAPLES Center on Feb. 8, 2015 in Los Angeles.

Boy Meets World star Danielle Fishel married Jensen Karp this past weekend (Nov. 4) and was lucky enough to have a special performer at her reception. John Mayer, a longtime friend and a groomsman at their wedding, sang a cover of Beyoncé's "XO" for the couple's first dance together.

Fishel noted that "XO" is one of the couple's favorite songs and that Mayer had performed it for them previously.