Famous for her moody frown, all eyes were on the Internet's favourite feline as she worked the red carpet in the camel-coloured Vivienne Westwood chapeau carefully balanced on one of her ears.
She was held by her owner Tabatha Bundesen and the pair rubbed shoulders with the likes of Emma Stone, Andrew Garfield, Johnny Depp and Cameron Diaz, who all attended the awards ceremony.
Host Conan O'Brien mentioned the Grumpy Cat during his opening monologue.
"Why does Grumpy Cat have a better seat than Nick Lachey? Nick, what the hell?" he joked. The excitement of the red carpet might have been too much for the cat – as the camera panned to her, she was fast asleep.
"I think it's easy to get to Jay Z right now than it is to get to Grumpy Cat."
Pharrell's hat has virtually become a celebrity in its own right since the singer wore it to the Grammys, sparking thousands of memes.
It was later sold for $44,100 at a charity auction to fast food chain Arbys, who use a design similar to the brown fedora. All profit went to Pharrell's charity From One Hand To Another.
Pharrell tweeted his thanks to the buyer, to which Arby's replied, "You're welcome. We're HAPPY to support a great cause & get our hat back."