ABC News' Linzie Janis reports:

Britain's Prince William and Prince Harry watched their close friend marry an American hotel heiress in Memphis, Tennessee, this weekend but it's the wedding's after-party that's getting all of the attention.

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The two brothers reportedly let loose at the wedding reception, held at the Memphis Hunt and Polo Club. Harry, according to some sources, was spotted twerking on the dance floor and William was spotted singing along to the live band.

"He came up on the stage and sung 'Shout' with me and danced with me," band member Jimmy Church said of Prince William. "They were singing, 'Shout, shout, shout.'"

William, 31, and Harry, 29, were celebrating after the Saturday wedding of their mutual close friend, Guy Pelly, a London nightclub owner, and Tennessee native Elizabeth Wilson, the granddaughter of Holiday Inn hotel chain founder Kemmons Wilson.

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The royals arrived in Memphis late last week and were greeted by throngs of screaming fans at nearly every turn.

"Harry was much cuter than I thought he would be, pure muscle," said Laura Fenton, a local fan who came out to see the princes.

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William - who traveled solo, without his wife and son - and Harry, who recently split with his girlfriend, Cressida Bonas, also took in some of the local sights and eats during their weekend trip to Memphis.

The duo was spotted Thursday night at Memphis' famous barbeque joint, Rendezvous, for dinner and also visited Elvis' home, Graceland, and the Lorraine Motel, where Martin Luther King, Jr., was assassinated.

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By Sunday, the wedding party was over, at least for Prince William, who was spotted boarding a commercial American Airlines flight to Dallas for the first leg of his trip back home to England.