Continuity mistake: Back at the police station from the hardware store, Cliff puts down a cardboard box full of stuff. He shows Mindy a couple of items, one being a funnel. He puts the funnel down, inside the box. At the next cut, the funnel is right on the corner of the box. (00:59:15)
Continuity mistake: In the car towards the end, Cliff has his hands crossed on the wheel, right hand on top. "May I ask you a question?" he goes. Cut to Adam Driver, and when the camera is back on Bill Murray, he is still leaning dejected, but with the left hand on top. (01:29:20)
Continuity mistake: The three kids in juvi are looking at the zombie horde press against the windows. Geronimo through the first phase (until the guard cries out "Save me!") has his hands off the top of the seat when viewed from behind, while his right hand is holding to it in front views. (01:06:15)
Continuity mistake: When the two dead golfers sit up, Tilda Swinton says "Good grief!" and places the green powder container on the magazine before pushing the chair back. In the overhead shot that follows, the powder moves to the table. (01:02:00)
Continuity mistake: At the police station, Ronnie gets up and switches the table lamp off when Mindy stands. Wrong continuity at the cut, though. Adam Driver still has the hand on the lamp, but his other hand is suddenly on the back of his own chair (it wasn't before), and Chloe Sevigny suddenly has her jacket in her right hand which was on the back of her chair. (00:20:55)
Continuity mistake: A couple times during the trip before stopping for gas as "The dead don't die" plays on the radio, Jack's arm moves from the top of the window to the bottom between shots (when the song goes "For the lights to shine down on" and when Zack passes him the energy drink). (00:39:15 - 00:39:50)
Continuity mistake: In the car after the visit to Hermit Bob, Adam Driver's radio microphone fights a constant battle for position between shots with his seatbelt. The most obvious bit is when he says "Yeah this isn't gonna end well", and the seatbelt is covering the radio. (00:06:20)
Continuity mistake: Zombie Iggy Pop approaches the counter to drink some coffee, and you can see a clock on the wall: it's approx 10:10. But as the zombies leave the diner, through the windows you can see the clock: it's now 9:25. (00:30:45 - 00:31:20)
Continuity mistake: In the motel room, Jack mentions "that Harry Potter guy at the gas station." Zoe's right hand is just below the left wrist. Reverse shot, and it's down at elbow level. (00:56:35)
Continuity mistake: At the diner, Farmer Frank is asked why he thinks Hermit Bob was the chicken thief. He puts the coffee mug down, but he already did that in the previous shot. (00:10:40)
Continuity mistake: Bill Murray and Adam Driver approach Hermit Bob's campfire; in the close-up, the skinned rabbit is laid out exactly the opposite way than in the wider shots - head to the right, legs to the left. (00:01:25)
Continuity mistake: Fern and Lily are dead on the floor of the diner, but the 'crowd' outside apparently can see them from windows that are roughly at the height of their heads, and keeping distant from the flower beds. Most curtains in that area were also completely pulled.
Continuity mistake: In front of the motel, Zack pulls the pink suitcase out of the trunk; he does it with Jack holding the bag high up, or all the way down in the second shot. (00:46:00)
Answer: It was in the script that they would die. Ronnie stated he knew it would end badly because the director gave him the full script ahead of time.
Invader_Gir