The former Spice Girls star is currently going through a messy divorce with husband Stephen Belafonte. But music mogul Simon appeared to have forgotten that fact as he quipped about her relationship status on Tuesday's episode.
After a performance in which one of the contestants had a technical error, Simon was asked what he thought of the performance, to which he replied: "I kind of imagine this would be like Mel B‘s wedding night. A lot of anticipation, not much promise or delivery."
As Simon made the joke, Mel looked outraged, before grabbing her cup of water and throwing it at her boss. She then walked off the stage.
While some viewers tweeted that they thought the situation may have been staged, the official America's Got Talent Twitter page quickly denied that, writing: "THIS IS LIVE TV, YOU GUYS. ANYTHING CAN HAPPEN. #AGT." They then added, "That was not planned, you guys. #AGT" and "This just in: @OfficialMelB has left the building. #AGT".
However, Mel returned to her seat on the judging panel before the next performer took to the stage.
She has yet to address her storming off on her own Twitter page, but her fellow judges reminisced on what had been the craziest America's Got Talent show to date after the programme had aired.
Howie Mandel, who judges alongside Mel, tweeted: "WOW. Tonight's live show was an adventure. Thanks for tuning in and tweeting with me, the #AGT results air tomorrow night."
And host Tyra Banks wrote on her Twitter page: "Tonight's @AGT live show was bananas. So much went wrong but that's what makes live TV so cray (crazy)!"
Mel and Stephen, the father of her five-year-old daughter Madison, are set to face off with each other at a trial on 25 September in which they will argue over her request for a permanent restraining order.
In her original filing, Mel listed a string of abusive behaviour including when she was forced to pull out of judging The X Factor in 2014 because Stephen had allegedly beaten her up and she overdosed on Aspirin. She was reportedly in hospital for two days following the incident.© Cover Media