Exclusive: Royal Wedding Reception Details

To be a fly on those palace walls!

Prince William and Duchess Kate's royal reception at Buckingham Palace was truly a night to remember. An insider tells Us Weekly about the night, right down to Harry's crack at William's bald spot and his own fiery tresses!

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"[Harry's speech] was hilarious," the insider says. "Everybody laughed. He made a joke about William wearing a thong under his uniform in the day. He made fun of how romantic William has been with Kate, and said that he knew it was a serious relationship with Kate when William, who does not have a romantic bone in his body, started being romantic."

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The 26-year-old prince even imitated the new Duke and Duchess's "baby talk" and "wanted to embarrass William." 

VIDEO: Watch William and Kate talk wedding -- and babies!

Harry "poked fun at [William's] bald spot, but said he can't talk because he's 'a ginge.'"

The red-headed man of honor added that their late mother, Princess Diana, would have been very proud of William and Kate on their wedding day. He added that William "is someone he has always looked up to and hopes to be like him."

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The newlyweds had their first dance to "Your Song" by Ellie Goulding. Towards the end of the song, William looked over to Charles, who stood up and danced with Duchess Camilla for a verse. Harry whistled loudly towards the end and everyone cheered.

When a guest congratulated Kate, the new Duchess said "she was just so happy and was doing her best to take it all in and just remember it. She laughed and said she was scared she would wake up in the morning and forget it all because it'd gone by so quickly."

Pippa Middleton, 27, was there without a guest or a boyfriend; Prince Harry, however, was seen dancing throughout the night with his on-and-off girlfriend, Chelsy Davy.

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At the end of the night, fireworks went off; the newlyweds shouted "Thank you, guys" to their remaining guests. The insider adds: "Everyone clapped and cheered when the fireworks went off. Harry did a 'wooooo!' Everyone was a bit tipsy then."

Commemorate Will & Kate’s big day with our Us Collectors Edition: Royal Wedding with all the photos, anecdotes and details of the wedding. Available for pre-order now and on sale May 6.