Continuity mistake: During the scene in the school corridor with Lucifer sitting down and talking to Chloe's daughter, the same extras keep doing erratic back-and-forth for no reason (for instance the girl with a white jacket and pink shoulder bag) or just plain wrong (the kid with the horizontal striped maroon sweater who walks twice past Lucifer early in the convo). (00:24:50 - 00:25:50)
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)
Continuity mistake: At the beginning of the episode, a cop pulls Lucifer over. The car stops with the front wheels on white road markings. When Lucifer is shown taking off again, the street is just not the same, there's no white horizontal lines, and a manhole appears under the car. (00:02:45)
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 ★