In 1982, during a weeks filming of the long-running series Fantasy Island, he tried to get his SAG card. Unfortunately for Firth, because he was being featured as a cave man, and primarily speaking in grunts and grumbles, the union didn't recognize his role as significant, and no membership was permitted.
In the entertainment business, I think you have to be like a spider - keep making the web, no matter how much it gets torn. It's unyielding persistence.