Robert Downey Jr. is having a grand old time these days. The mercurial actor not only starred in the box-office sensation " Iron Man ," he now has a spectacular scene-chewing role in "Tropic Thunder," the new No. 1 film at the box office (and recent Public Enemy No. 1 to protesters ). Downey is a wonderful nut, an American treasure as far as I'm concerned, and I can tell you firsthand that interviewing him is a dizzying and exhausting experience. The man is one relentless riff. Take this tongue-in-cheek rant I just read over at indelicately named website Moviehole.com : "My whole thing is that that I saw 'The Dark Knight.' I feel like I'm dumb because I feel like I don't get how many things that are so smart. It's like a Ferrari engine of storytelling and script writing and I'm like, 'That's not my idea of what I want to see in a movie.' I loved 'The Prestige' but didn't understand 'The Dark Knight.' Didn't get it, still can't tell you what happened in the movie, what happened to the character and in the end they need him to be a bad guy. I'm like, 'I get it. This is so high brow and so f---ing smart, I clearly need a college education to understand this movie.' You know what? F--- DC comics. That's all I have to say and that's where I'm really coming from." Was he serious? I doubt that. I know Perez Hilton and his readers are taking this as gospel, but they weren't sitting at the Warren Beatty tribute a few months ago when RDJ w ...