The oversized midi dress with giant white polka dots was topped off with purple feathers.
Katy matched the dress with a long orange wig, complete with multiple top knots and purple drop earring and matching eye shadow.
The expectant mom captioned the post: "🍊 Orange you glad TODAYS THE DAY! 🍊 Hope you enjoy my �� (big) top tier 🎪 performance at @Tomorrowland Around the World 🌍 the digital festival - 12.50pm PDT / 3.50pm EDT / 21h50 CET – info & tickets: tomorrowland.com or at the link in my bio."
Her post also included the beginning of her performance which sees her perform in a CGI hot air balloon in the shape of a clown's face.
The Tomorrowland digital festival running this weekend is an unique online pay-per-view experience of nine hours per day of entertainment.
The interactive festival guides viewers by a magical 3D map where they can discover unseen stages and an endless list of surprises.
Katy's performance could be one of her last before she gives birth to her first baby with fianceé
With the imminent arrival of their newborn, Katy was busy swatting rumors about the baby's potential godparents.
She addressed Jennifer Aniston will be godmother to her baby girl.
Katy told Australian radio show Kyle and Jackie O said she had "no idea" where the rumor came from.
"I guess it's a fun rumor," she said.
"We have no idea where it came from. That is the product of the media and the internet!"
Katy, 35, also opened up about her pregnancy journey and admitted it has given her "a whole new viewpoint".
She explained: "I'm really grateful for my body.
"Going through this process you get a whole new viewpoint."
The pop star said she's now at the point in her pregnancy where "everything is swollen."
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She said: "My hands are swollen, my feet are starting to swell."
Katy also revealed she's been busy "putting out songs and heading towards putting out a record."
She said: "I'm a very active woman and during this time of COVID, and quite frankly an American revolution, I have been also putting out songs and heading towards putting out a record.
"I'm working really hard. The one blessing is I don't have to travel extremely.
"I like not watching the hands of time roll by. I like being a mother on the move."