Revealing mistake: When all the vampires are saying "for the dark", and one gets staked, there's a mark on his shirt where the stake's about to come through before it actually happens. Plus Buffy's hands are in the wrong place for her to have pushed that stake through, as well as there being no stake in her hand when the vampire gets dusted. Not only that, but the mark isn't even close to the vampire's heart to begin with. (00:34:50)
Continuity mistake: When the sarcophagus explodes, the blast door they escape through has no card reader. Once they stand up it's there. (00:37:55)
Young Kidaichi's Murder: File 1 - S2-E1
Other mistake: Kindaichi escapes handcuffing the detective to the toilet's chain. Try to think of the last time you went to a restroom and the chain was SO long that you could yank it across the whole room (not stall, room) and outside the door. Going behind the sink's drain, even. Never seen a toilet like this in my life (and in that kind of bathroom, you have usually buttons or pedals, anyway). (00:21:00)