Katy Perry Says She Loves 'Sweetheart' John Mayer

Katy Perry dished on her on-again main squeeze, John Mayer, at the Westwood, Calif. premiere of Smurfs 2, telling Nancy O'Dell that she loves the rocker.

When Nancy mentioned John dedicating a song to Katy, she replied, "He is a sweetheart. That's why I love him."

John wasn't Katy's date to the premiere, but she brought someone equally special -- her 92-year-old grandmother, Ann Hudson, who stole the show on the blue carpet.

While the pop star, who plays "Smurfette" in the animated sequel, was posing for photos, her grandmother was doing her own press, having a chat with ET's Nancy O'Dell about her famous granddaughter.

PICS: Katy Perry & Britney Spears at 'Smurfs 2' Premiere + More Star Sightings

Shortly after Mrs. Hudson, who donned an "I've got the hots for Papa Smurf" shirt to the premiere, praised Perry for being a great grandchild, the 28-year-old singer joined the interview and jokingly said, "She's already taking the spotlight from me. You bitch!"

Perry explained that she and her grandmother, who recently relocated to Los Angeles from Las Vegas, have an "interesting relationship" in which her grandmother occasionally jokingly calls her derogatory names as well.

As for the reason she (or her grandmother) was doing press to begin with, the "Part of Me" talked about how she landed her role in the animated film franchise, which she first voiced in 2011 for the first Smurfs film.

VIDEO: Katy Perry: 'Smurfs 2' is 'Really Heartfelt'

"Anonymously," Perry revealed. "I guess they heard a snippet of my voice, maybe from me doing interviews just like this. They didn't know it was me and they heard it and said it matched perfectly for Smurfette."

While Perry's role stretches outside of her niche, ET's own Nancy O'Dell holds a role in the film that very much fits into hers: herself. After recently playing herself on the TV series 90210, Nancy plays host of an entertainment news show inside the Smurfs universe.

"I have to say, it was quite the stretch to play Nancy O'Dell," she joked. "I really had to channel my inner self to try and come up with who I'm supposed to be."

VIDEO: Nancy O'Dell's '90210' Debut

Check out the video for more from the Westwood premiere of Smurfs 2 (in theaters Wednesday, July 31), including interviews with Neil Patrick Harris, George Lopez, and Jayma Mays.