2. The Undertaker Wasn't Supposed To Bleed
Not everything went right during the extended shooting session.
The Undertaker decided to re-shoot his hearse window attack from a different camera angle, and accidentally ended up smashing the glass. After some deliberation from the crew (they toyed with the idea of flipping the car around so they had fresh windows), everyone decided it looked cool and that they should keep that shot.
The blood that spilled from 'Taker's arm following his spiked strike wasn't intentional. Rather than pausing to bandage him up though, WWE kept filming and liked everything they captured. Eventually, the blood wasn't even an issue, and some thought it added to the spectacle.
They were right. It's amazing to think that the stunt staff were ready to turn the hearse around so fans would be none the wiser and try again. The little hints of bloodletting on offer fed into the narrative that this was an intense brawl between two men who couldn't stand one another.