Katy Perry Jay Leno autographs

Yesterday, Katy Perry was as happy as can be outside of the NBC Studios, taking pictures and signing autographs with her faithful fans.

On the show, the Wide Awake singer discussed a deal of topics, one of which being her preparation for Vogue magazine's July issue photo spread that was shot by famed photographer Annie Leibovitz.

"I did a lot of my own prepping. I kind of went on a cleanse... I did a lot of stuff like vitamins and supplements, I changed my coffee to green tea, I didn't drink alcohol for three months," the 28-year-old pop star told the late night host. "I was really in the zone, I just wanted to be glowing for that cover."

From the looks of things, it seems all her hard work paid off!