Perry, who had the most nominations coming into the show with 10, came away with three moonman trophies, including video of the year for the inspirational clip "Firework."
"I feel like I'm doing something right when I sing that song," said Perry, conservatively dressed in a cotton-candy pink jacket, a skirt and something best described as a Green Bay Packers cheesehead decoration.
But the night's big news came from Beyonce, who stole the show before it even began when she announced on the black carpet that after more than three years of marriage, the dazzling couple had produced the ultimate all-star collaboration. Dressed in a loose-fitting, off-the-shoulder red gown, she clutched the baby bump that so many celeb-watchers had been predicting since the two wed.
Later, Beyonce performed "Love on Top," and if Twitter hadn't already spread the news, her outfit gave clues to her impending motherhood; instead of her typical sexy outfits, she dressed in conservative spangled tux - but still danced around in her signature stilettos.
Beyonce didn't utter a word about the pregnancy, but ended the number by taking off her jacket and rubbing her swollen belly; in the audience, an elated Jay-Z hooted and clapped for his wife as Kanye West hugged him.
In an instant, Beyonce and her soon-to-be child managed to overshadow the night's events. Lady Gaga's much-hyped opening number, during which she performed as a greasy, leather-jacketed male alter-ego during a performance of "You and I," became less interesting. So did the evening's meticulously planned wild moments, from Nicki Minaj's origami-like outfit to a dance-off between the members of Odd Future and Jack Black, Will Ferrell and Seth Rogen.
There was one apparently unscripted moment during Jay-Z's performance with Kanye West of "Otis," off their chart-topping joint album "Watch the Throne." Near the end of the song, someone tried to walk on the stage, but was quickly apprehended by a crew member as a bemused Jay-Z looked on. It was the second time Jay-Z had someone walk on unannounced during an MTV performance; two years ago, it was Lil Mama.
Britney Spears captured the night's first award, for best pop video, and later was honored with an MTV Video Vanguard award for her visual legacy. Lady Gaga, sticking to her gender-switch shtick, leered at Spears as she paid tribute to her.
"She's a pop music legend, and the industry would not be the same without her," Gaga said. "I used to hang pictures of her on my wall and touch myself when I was in bed."
Later, Gaga fished for a kiss, but as Spears leaned in, she quickly pulled back, reminding viewers, "I've done that before."
The show at the Nokia Theatre in Los Angeles had no official host, though comedian Kevin Hart delivered an opening monologue and was featured in a series of vignettes during the show.
Adele had perhaps the highlight of the night as the seven-time nominee delivered a powerfully understated performance of "Someone Like You," off her top-selling "21" album.
Chris Brown also wowed with an aerial number, soaring above the crowd in between high-stepping choreography.
Russell Brand provided the evening's rare poignant moment during a tribute to his late friend, Amy Winehouse, who died a month ago after struggling for years with drug and alcohol abuse. Brand urged people to remember the 28-year-old for her music, and urged others suffering to get help.
"A lot of people just get the disease, not many people get the incredible talent that Amy was blessed with," said Brand, who successfully battled drug addiction himself. "Let's remember there is a solution ... that solution is available."
Tony Bennett, who joined Winehouse in what is believed to be her last song on his upcoming "Duets II" album, showed the audience a clip of the pair singing "Body and Soul."
Moments later, Bruno Mars sang one of her hits, "Valerie," but closed the song out with the refrain, "Amy, we'll miss you baby," as a somber-faced audience looked on.