Sweet Kicks - S1-E5
Continuity mistake: The position of the guys Mazikeen attacks changes between shots. Note the woman Chloe knocks out. (00:31:30)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: When Lucifer shows his devil face to the preacher at the start, the mascot behind Lucifer changes between shots. (00:03:00)
Sweet Kicks - S1-E5
Continuity mistake: When talking to Benny about his pig being killed, Benny's hair is constantly changing from neat to scraggly and back. (00:24:30)
Favorite Son - S1-E6
Continuity mistake: Near the end, as Lucifer is bearing down on the biker asking who took his wings, the Biker stumbles and has both hands behind him. When the shot changes his left hand is raised. (00:33:40)
Favorite Son - S1-E6
Continuity mistake: At the start when the security guard is attacked, the number of papers thrown about changes from 5+ to 3. (00:02:40)
Sweet Kicks - S1-E5
Continuity mistake: When Chloe and Lucifer get in the car to go to a bar, the car's position in the alleyway changes from the street level shot and the overhead shot. Note the position in relation to the plant by the side of the car. (00:12:10)
Continuity mistake: At the start when Trixie comes running in to give Lucifer a hug, Lucifer has got a jar in his hand. As the shot changes to him actually being hugged, the jar simply vanishes from his hand. (00:03:05)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: In the interrogation room with Nick, more than once (for instance when Lucifer says at the beginning "I don't want to know about the case") when Jeremy Davies lifts his open hands and holds them up, they are held up at a different height between one shot and the reverse. (00:18:50)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: The fake preacher runs away leaving all the money behind: in the overhead shot Lucifer says "I'm here till, well, the end of times actually" turning around past a guy (big hair, big sideburns, black and blue shirt) that he already passed in the shot before as he thanked the crowd. (00:03:20)
Continuity mistake: Lucifer walks down the stairs into 2 Vile's mansion; first person he comes across is carrying a glass, wearing a black T-shirt and grey undershirt sticking out. The guy is walking towards Lucifer as if he were going to use the stairs Lucifer is descending, but just vanishes in the following shot, only to reappear at the next cut, taking the stairs as it seemed bound to happen all along. (00:16:15)
Continuity mistake: When Lucifer talks to the killer in agony in the car wreck, blood streaks change on his face between shots (in particular, he has blood coming from the corner of his moith in the last shot, from the side, but he had none a moment before, in close-ups). (00:09:40)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: Immediately after the close-up on the poster of Demon Town with Penelope Decker, Lucifer holds the trophy. From behind it's evident that Chloe's healthy arm is down her side, but in the reverse shot she has her arms crossed. (00:17:30)
The Would-Be Prince of Darkness - S1-E3
Continuity mistake: Chloe takes the phone in Lucifer's hand as he is watching the registration. Depending on the angle Chloe has her right hand on the phone itself or off it, signaling Lucifer to stay put. (00:13:15)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: Talking with her daughter at the end of the episode, Chloe stifles her laughter with her hand in front of her mouth. In the matching reaction shot her hand is still on her chest. It happens again twice. (00:40:30)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: When Chloe asks Jimmy about Lucifer at the end of the episode, her good arm is down her side when seen from behind, or folded in the frontal views. (00:42:25)
Answer: Boo Normal and Once Upon a Time were going to be part of season 4, then the show got cancelled (before being picked up elsewhere). As such they were added on to the end of season three as "bonus" episodes, hence the continuity being off. But not really a mistake, just a quirk of broadcasting. Boo Normal was originally going to be between the episodes "High School Poppycock" and "Infernal Guinea Pig" in season 3 before being slated for season 4, presumably because aside from the point you've raised, it was fairly flexible, continuity-wise.
Jon Sandys ★