For American Idol season 20's Disney Night, judge Katy Perry wore an Ariel costume from The Little Mermaid, and she gave a behind-the-scenes glimpse of how she put the elaborate outfit on. Each year, fans look forward to seeing who Katy will dress up as for Disney Night. Her past costumes include Snow White, Ursula the Sea Witch, Mrs. Jumbo and Tinker Bell. For American Idol season 20, Katy's costume was as outrageous as ever, with a plastic wig of red flowing hair and a sea foam green mermaid tail. She carried a fork, or "dinglehopper," as Ariel would call it.

Because of her fin, Katy could not walk out onto the stage, so her fellow judges Luke Bryan and Lionel Richie had to wheel her out on a dolly. When she got to her seat, host Ryan Seacrest began to talk about the Top 10 finalists, but viewers heard a loud crash off-screen. It turned out that Katy had fallen backwards in her chair when it tipped over. As everyone laughed, Luke, Lionel and Ryan helped a thankfully unharmed Katy back into her seat.

Related: American Idol: Luke & Lionel React To Katy Perry’s Disney Night Fall

In a post on Instagram, Katy gave her followers a glimpse behind-the-scenes with a post that explained how she got into her costume. As her little dog looked on, dressed as Ariel's fish pal Flounder, a team of five people helped Katy put on her fin. Katy was on the floor as they attempted to squeeze her legs into the tail. One of her helpers jokingly told her to "push" as Katy announced that she had gotten one of her legs into it. She captioned the post, "Some BTS of a lil Sunday sushi."

Katy elaborated on the process of getting into her American Idol Disney Night costume in an interview with ET. She revealed that she was covered in oil in order to help slide into the costume. When Luke and Lionel wheeled her out on the dolly, they realized how slippery she was. Katy joked in character as Ariel, "I don't have those things that people call 'feet.' So, yes, I had to come out in a dolly. And Luke was helping me, and Lionel was holding my fin. And I was a little slippery. They didn't really like it. It was getting all over their really expensive clothes." Katy said that it was "super fun." She also shared that her 1-year-old daughter, Daisy, has just started to watch The Little Mermaid and that she wanted to FaceTime her in her costume before she went to bed.

Katy's Ariel costume on Disney Night, which featured mentor Derek Hough, was perhaps the most outrageous yet. Between her inability to walk and her fall, she even had to be wheeled onto the red carpet. This costume created a lot of memorable moments on American Idol Disney Night. Katy is always a good sport and does whatever she can to entertain the audience. She is one of the reasons that Disney Night has been such a success on American Idol.

Next: American Idol: How The Top 10 Spent Their Days At Disneyland

American Idol airs Sundays at 8 p.m. EDT on ABC.

Sources: Katy Perry/Instagram, ET/YouTube