Continuity mistake: After Buffy finds Morgan's brain, Willow pulls up Morgan's school file on one of the library computers without even touching the keyboard. One moment the monitor is on the desktop, the next it's showing Morgan's file.
Continuity mistake: Carter and Cadet Haley enter the Stargate and we see them through the "puddle." When they come out on The Other Side, their positions are reversed.
Beware the Third Wish - S1-E31
Continuity mistake: The Wicked Wisher throws giant exploding coins onto the field TJ is on, as TJ runs towards the WW. The giant coins remain on the field after they explode, yet when TJ reaches the top of the field, there is no sign of the coins, or their remains.
Gentleman Thief's Murder: File 1 - S1-E10
Continuity mistake: When the painting pops up with the card of the real Kaitou Gentleman's card on it, the card is placed on a different spot in the different shots. (00:11:55)
Continuity mistake: When King mentions the two brothers' "destiny", his big feline is at Young Diabolik's side, facing King and the others. Aerial shot, and the panther is at King's side facing Diabolik. (00:05:00)
Continuity mistake: The fish that Harley uses to protect herself from the Joker changes shape and size every shot.