"Look I don't want to talk long because I have never been the warm-up act for Katy Perry before," President Clinton told the crowd from a parking lot in downtown Des Moines ahead of the Iowa Jefferson-Jackson Democratic dinner. "I am well aware I am the warm-up act."
"There's been a lot of talk about breaking the glass ceiling. And I want to talk about one barrier that has not been broken," he said to the crowd of more than 4,000 people. "I want you to support Hillary for me, too. Because I want to break a ceiling."
Clinton then mentioned the "11-hour marathon in Washington" on Thursday.
"We had the friends of our lifetime, Hillary and I did, e-mailing me furiously saying they thought she was doing great and all that. To every one of them I wrote back a simple answer: I think I'll vote for her. And that's what I want to say to you, all of you," he said.
At one point an animal rights activist interrupted Clinton, who played it cool and kindly asked the protester to stop.
"Will you please quit now? Thank you," Clinton said as the crowd chanted "Hillary! Hillary!"
Following the former president's remarks and introduction, Katy Perry took the stage singing "Roar," a song that is a staple on Hillary Clinton’s campaign playlist.
"You ready for a better future?" Perry yelled out. "All the way back home you are going to hear us roar to 2016 and beyond."
Perry's set also included "Wide Awake," "America the Beautiful" and "Firework."
"She is my firework," Perry, who was dressed in a white dress with a "H" logo on it and an American flag cape, said about Clinton.
The Democratic frontrunner then joined the pop star on stage for a surprise appearance.
"Sometimes it's important — you just have to roar about what you need to fight for," Clinton said after embracing Perry in a warm hug.
Two people dressed as "Left Sharks," the character made famous from Perry's Super Bowl performance, were outside the event waving Sanders signs. And throughout the entire program, even as Clinton spoke and Perry sang, an airplane carrying a pro-Sanders banner circled overhead.