In a 2002 comic book, eight years before Christopher Nolan's little dream exploration film, Scrooge got his mind hijacked by the Beagle Boys. The Boys were trying out new careers as dream-thieves and went into Scrooge's mind to steal the secret combination of his vault. If this sounds vaguely familiar, it's because that's exactly how Inception opens up, except you have to replace DiCaprio with talking dogs. Which, incidentally, would probably improve every single one of his movies.
After they're inside Scrooge's mind, the Beagle Boys have trouble differentiating dreams from reality -- again, exactly like the characters from Inception, who need special items, or "totems" in order to tell dream from reality.