But the racy dress-up didn't, ahem, end there. Perry, 25, also revealed the name "Rusty" – stitched in silver letters – on the back of her knickers. FYI: Rustyrockets is Brand's Twitter sign-on.
Brand, 34, clearly approved. "Wow," he Tweeted. "Now MY GIRLFRIEND has worn a West Ham basque while hosting the EMA's. What a day!"
He added: "Yes I will be taking her to a game – West Ham Vs Everton." That will take place on Sunday.
In the meantime, this may be the most public example yet of the couple's blossoming romance. Over the last month, they have hung out in Paris during fashion week and in London before they headed to Los Angeles.
The singer's tribute to Brand and West Ham was, in fact, one of her 12 costume changes during the awards show.
Not to be outdone, Beyoncé Knowles wore a racy red basque to perform at the show, where she also came out the night's top winner. Her three awards were for best song ("Halo"), best video (for "Single Ladies") and best female artist.
She dedicated her video prize to her husband, saying: "There's only one person I want to thank, and that is Jay for putting a ring on it."
Male artist honors went to Eminem, while best live act winner U2 performed outdoors at the city's Brandenburg Gate, to mark the 20th anniversary of the fall of the Berlin Wall.