Following the show, she headed straight to the L'Ermitage Beverly Hills Hotel to perform at the Interscope Records fete that included such other famous faces including Jay-Z, Beyoncé and Kim Kardashian.
So what was Gaga's outfit and song of choice?
"She was wearing basically underwear—a bra and tiny shorts" a source tells me, adding that Gaga didn't appear to have a date at the bash.
Although her Grammy performance was in her typical over-the-top style, she was more understated at the Interscope shindig. "She came up to the piano and sang a slow ballad that wowed the crowd," the source says.
Later in the evening, Snoop Dogg and Dr. Dre took the stage, rapping hits like "Gin and Juice" and "Nothing but a G Thang," but their performance got quieted when neighbors complained about the noise around 2 a.m.
Across town, Nicole Kidman and Keith Urban stopped by the EMI postparty, where Nic posed for photos with fans. While Nic and Keith were totally coupled up, one VIP's famous hubby was MIA from the bash.
After walking the carpet with Russell Brand and her grandma and sharing video from their wedding during the show, Katy Perry rolled solo to the Ultimate Ears-sponsored soiree at Milk Studios. Apparently, Russell was too jet-lagged after hosting SNL the night before to attend.
"He was really tired since he just flew in from NYC yesterday," a source tells me.
Not that Katy seemed to mind. She hung with her stylist Johnny Wujek and a bodyguard as fellow guests sipping Patron Tequila tried to sneak a peek of the pop star.
—Additional reporting by Dan Wally