The 63-year-old Dutchman clipped assistant manager Ryan Giggs around the ear after the Welshman outbid him for a round of golf with former United striker Dwight Yorke during an auction at the event on Tuesday.
He then took to the stage to deliver a rambling seven-minute speech, at one point punching the air and roaring “Yes!” as he recalled a team meeting at which captain Wayne Rooney had urged the team to push for second place in the Premier League.
Van Gaal also said that United had been “very close” to winning the title, despite the fact they currently trail champions Chelsea by 15 points.
After concluding his speech, which was broadcast live on United’s in-house television channel MUTV, Van Gaal returned to the stage and interrupted the presenter by saying: “Hello, hello! Pay attention to the manager!”
He went on to chastise the crowd for not applauding a female saxophonist, saying: “I have seen a lady who plays the saxophone fantastically. Give her a big applause!”
Former United captain Gary Neville tweeted: “LVG is cracking me up here. Great entertainment! One of the best/funniest 20 mins I’ve ever had!”
United goalkeeper David de Gea, who has been strongly linked with a move to Real Madrid, won both the Players’ Player and Fans’ Player of the Year awards for the second season running.