"She's a normal cat. She's really sweet," Bundesen tells PEOPLE. "She sleeps like 18 hours a day."
Real name Tardar Sauce, Grumpy Cat became a phenomenon when Bundesen's brother Bryan posted a photo of her on Reddit.
"We thought it was so grumpy, we had to share it," he says.
Though the attention has brought her a growing fan following, and a new campaign with Friskies, Grumpy Cat hasn't turned that frown upside down – yet.
"No. Grumpy Cat doesn't smile," Bundesen says – until PEOPLE Pets got ahold of her.
Watch the video above to see if we made Grumpy Cat smile.
See more amazing animals in this week's issue of PEOPLE, on newsstands Friday!