Douglas Mills Jr. and Scarlet seemed like a total mismatch and provided some of the most dramatic moments of the show.
"We are pretty much nothing alike," Scarlet said.
Douglas could not remember his lines to their song "Rewrite the Stars" and at one point, Scarlett stormed off.
"It's hard for me to learn songs really quickly," he said.
Scarlet blamed her reaction to his struggles on bad past experiences with other singers.
While they worked it out, when the couple hit the stage Douglas stumbled through the song.
"Death by song," Katy Perry said. "That song was not the right song. We could tell you didn't really know it."
Despite their struggles, Katy said they were moving forward thanks to "some moments in the past and how beautiful they were."
Christian Guardino and Nicolina delivered what might have been the duet of the night with their performance of "The Prayer."
"I have to tell you when you can stand on a stage under pressure and we're mesmerized just watching how you play off each other, it has all the makings of something so special," Lionel Richie told them after the performance.
The contestants don't have a lot of time to prepare for the duet once they learn who is their partner. Some of the contestants worked late into the night trying to get their act together.
"I am so tired," Cole Hallman said after a long night of rehearsing with Cadence Baker.
They sang 'How Sweet It Is' by James Taylor, but their performance was, in Luke Bryan's opinion, "underwhelming" compared to their previous appearances.
Cole admitted his voice is going and the judges decide that he has reached the end of his Idol journey.
Perhaps the most inspiring moment of the night came when Kelsie Dolin, who is harmonizing for the first time and has no experience on stage, was partnered with former Miss America Betty Maxwell.
Kelsie has lacked confidence throughout the season despite continuing to advance.
"You are such a diamond in the rough. All you've gotta do is shake off that dust," Katy Perry told her.
Betty worked with Kelsie on choreography and harmonizing hoping to build up her confidence, but was admittedly nervous going into the performance.
Their duet of Pink's "Just Give Me a Reason" moved Lionel Richie to tears.
"I was worried for a moment because I thought you were not going to rise to the occasion," he said. "You broke through. You were harmonizing and attitude and choreography and who the heck are you now?"
Katy Perry applauded Betty for drawing out the best that Kelsie could be.
You can see more of the duets from the show streaming now on Hulu.
The search for the next Idol continues Monday night with the showstoppers round as contestants take the stage for the first time with a band and the field narrows to the top 24.
Watch the next American Idol on Monday at 8 p.m. ET/PT | 7 p.m. CT on your local ABC station and the next day on Hulu.