Back on Katy's page, the hacker sent off a series of vulgar and nonsensical tweets, including, "otf gang n**ga!", and "u a f** @keemstar," mentioning a blogger with more than 80,000 followers on the microblogging site.
The user also wrote, "miss u baby @taylorswift13," which seemed to be an attempt to reignite a reported rivalry between the two entertainers.
Perry and Swift famously fell out in September, 2014, after the Style singer revealed her song Bad Blood was inspired by her feud with another female artist.
"For years, I was never sure if we were friends or not," she told Rolling Stone magazine at the time. "She would come up to me at awards shows and say something and walk away, and I would think, 'Are we friends, or did she just give me the harshest insult of my life?"
Rumours quickly emerged she was talking about Katy. Swift didn't respond to the fake tweet, which was deleted with the other hacked posts minutes after they were published.
Perry's last real tweet came about five hours prior to the takeover, when she re-posted a message from US presidential candidate Hillary Clinton, who remembered fallen veterans on America's Memorial Day.
Clinton wrote, "Our fallen heroes deserve our profound gratitude for giving their lives to protect our freedom, today and every day. #MemorialDay." Katy added, "Yes! Thank you to the heroes we've lost and still serving! We appreciate you and honour you today!"
- WENN