Revealing mistake: Mr. & Mrs. Castle wish for a million dollars in 5 and 10 dollar bills. But the bills they receive all have the same pattern printed on both sides, a pattern which which doesn't resemble any real US currency. There's also not nearly enough of the bills to total a million dollars.
Revealing mistake: The main character's reflection in a mirror has come to life and much of the episode is a confrontation between the character and his reflection. Although they made an effort to reverse the image (the reflection wears his watch on the opposite hand and he bites his fingernails with the opposite hand) they forgot to reverse the buttons on his shirt.