The singer and the actress chatted over Instagram Live on Monday.
The virtual chat came several hours after the release of Perry's new music video for her song "Not the End of the World."
In the video, which stars Deschanel, extraterrestrials -- who are also huge Katy Perry fans -- kidnap the New Girl actress thinking she's the pop star.
The music video is a fun tongue-in-cheek reference to the fact that both Perry and Deschanel are always said to be lookalikes. As Perry revealed during their chat, it's a truth that she used to use to her advantage.
"When I moved to L.A. maybe 18 years ago... I was pretty much a nobody, and you were like just getting so huge at that time, it was like Zooey Deschanel ran the world," Perry explained. "In that moment, I was so complimented to look like you."
"But I have to admit something to you," Perry continued. "When I first got to L.A., I went to the club. A lot. And I wanted to get into the club, but I had no money, I had no clout, I had nothing, and sometimes I would pose as you to get into the club."
To Perry's shock and embarrassment, Deschanel responded, "Well, I know this."
"People were like 'I saw you!' But I'm such a goody two-shoes, and people kept going like, 'I saw you out! I made eye contact with you!'" Deschanel recalled with a laugh. "Then everybody kept telling me about you, 'This girl Katy, she looks just like you,' and I'm like, 'Who is this Katy?'"
"And then when I first met you, I was so relieved because you're so pretty, and I was like, 'Oh, thank God. She's so pretty,'" Deschanel added.
Perry went on to explain that, when she was in the clubs, she was "tuned up to 11," and was particularly wild.
"So I'm sorry if I misrepresented you," Perry added, as a smiling Deschanel told her not to worry, and that the confusion was just a compliment.
Perry's latest music video comes after welcoming her baby daughter, Daisy, with fiancé Orlando Bloom back in August. Perry, playing herself in the music video, is seen pushing her baby around in a Minnie Mouse-themed stroller.
Check out the video below for more on Perry's adorable new bundle of joy.