The 26-year-old singer dressed in a glowing futuristic outfit and led a group of alien dancers as she performed her #1 smash.
“#ET ON AMERICAN IDOL TONIGHT!” Katy tweeted right before the show.
Katy was joined by Kanye West, who she watched over the weekend at the Coachella Music Festival.
She tweeted, “and then Kanye played all the hits and we were #living!”
WHAT DO YOU THINK of Katy’s performance?