She joined the group decked out in a giant afro wig. Following her surprise appearance, the singer tweeted, "I just played with Queen I'm the happiest girl alive," then Instagrammed several pictures of herself along with guitarist Brian May and Lambert.
I just played with Queen I'm the happiest girl alive! #QAL
— Lady Gaga (@ladygaga) August 27, 2014
My stick selfie of the day - with our lovely guest Lady Gaga XXX BRI pic.twitter.com/UOrIQhjemn
— Dr. Brian May (@DrBrianMay) August 27, 2014
Gaga also revealed on social media that May and Lambert had been to her artRAVE ball. "I’m so PROUD of Adam Lambert singing with them," she wrote. "Made me cry during Dope when I saw them all sitting there. ... I thought about Freddie.”
Owing the ultimate homage to "Tonight I felt alive in a way I have not before," she continued. "I returned to the Radio GaGa mothership to pay homage to my leaders. It was emotional and wild."
Watch a video of the performance below:
This article originally appeared in THR.com.