Prince William stood at his younger brother Harry's side as he said his wedding vows and married Meghan Markle.
And just like any other good Best Man, Wills got up during the private evening reception and told a few embarrassing stories about the groom.
While Harry's infamous playboy days were off-limits, he cracked a lot of jokes about Harry's hairline.
And while you might expect the second in line to the throne to be a safe bet when it comes to well-behaved jokes, William actually made a surprisingly "filthy" joke, and it was about wet knickers.
One guest told the Sunday Times that Wills joked about "wet knickers" during his time with the mic.
Unfortunately details of the joke haven't been leaked - but we really hope we find out at some point!
William also pulled a prank on his little brother at the party, and nearly "floored" some of the guests in the process.
Apparently Harry fell off a ladder while trying to change a lightbulb a few weeks before the wedding, so Wills tied a ladder to the back of the newlyweds' car.
Harry's pal Charlie van Straubenzee also gave a speech during the celebrations, and spent most of it mocking the prince for his ginger hair.
According to the Times, he questioned Harry's behaviour when he was acting as dorm monitor at Ludgrove School in Berkshire, where they were both students.
He said: "All I wanted was a cuddle from my mummy.
"Instead Harry nicked my teddy bear and chucked it out on to the roof.
"Ladies and gentlemen, I ask you, how can you put someone in charge of a dorm when that someone is worse behaved than the whole dorm combined?"
The bride and groom also made speeches during the evening reception at Frogmore House in Windsor Castle.
Harry reportedly moved guests to tears as he gushed over his new wife and paid tribute to her mum Doria.
Meghan read an emotional love poem and declared she had finally "found her prince".