Mickey Rourke

Mickey Rourke is mourning the loss of his best friend — his longtime pet Chihuahua, Loki. The canine passed away Monday evening at the age of 18, E! Online reports.

Loki, who's been the Oscar nominee's sidekick to various events, including the Venice Film Festival red carpet, was one of the pooches memorably thanked by Rourke when he won his Golden Globe for The Wrestler last month.

"I'd like to thank all my dogs, the ones who are here and the ones who aren't here anymore," he said. "Sometimes, when a man is alone, that's all you got is your dog. And they've meant the world to me."

Rourke has credited his canine companions with sticking by him during career low points. "I sort of self-destructed and everything came out about fourteen years ago or so... the wife had left, the career was over, the money was not an ounce," he told Barbara Walters for her annual pre-Oscar special. "The dogs were there when no one else was there."

The dog lover has also been a vocal advocate of animal causes, most recently posing in a "spay-and-neuter" PETA ad with one of his pups, Jaws.