Gaga and Wonder served up a duet of the Hotter Than July track, with Gaga occasionally modifying the lyrics from "Happy birthday to you" to "Happy birthday Elton" for the occasion.
John's 70th birthday bash at Red Studios was a star-studded affair with a guest list that included Gaga, Wonder, Katy Perry, Jon Hamm, James Corden, Rob Lowe, Roseanne Cash and many more.
The party, which doubled as a celebration for the 50th anniversary of John's partnership with songwriter Bernie Taupin, benefitted the Elton John Foundation and the Hammer Museum at UCLA, People reports.
In addition to the "Happy Birthday" duet, Gaga performed a piano-only mini-set that included hits like "Bad Romance" and "Born This Way."
Speaking to Beats 1 Radio's Zane Lowe earlier in the week, John said of his upcoming 70th birthday, "Some people don’t like birthdays, they don’t like celebrating, they don’t want to know about them, and I’ve always enjoyed my birthday… Seventy sounds so archaic, doesn’t it? When I was growing up, 70 sounded like the end of the world. But things have changed — you’re only as old as you feel inside."