Other mistake: When Durant uses his cigar cutter to cut off Eddie's fingers, no blood is shown squirting from his severed digits and no blood is seen on the cigar cutter. (00:05:15)
Other mistake: Near the end, when Julie is pushed off the building by the henchmen, her handcuffs get caught on some rods that where sticking out. But this is impossible, by the way she was falling (vertically) the rods would have made contact between her legs. No way her handcuffs could have been caught like that. And they were sticking out a good foot or two from where her body was.
Other mistake: Julie is standing 2 meters away from the building when it explodes. We see tons of glass, wood and burning debris fall everywhere, but not a single spark touches her. She remains spotless and immaculate despite the havoc.
Other mistake: Just before the Strack helicopter which Durant is in hits the bridge, the letter and numbers painted on the side just forward of the cockpit door are backwards, like a mirror image.
Answer: It's just psychedelic imagery to try and show his fragile state of mind and how he's losing it. The shattering light-bulb is likely to show that his mind is "shattering" (as light-bulbs appearing above someone's head are often used to signify brains/ideas in fictional, particularly cartoons), and the marionette "dancing" is the first part of the recurring motif in which he sees himself as a "freak." (Which is paid off later when he starts singing a demented song about "Paying five bucks to see the dancing freak!").