Revealing mistake: The fractal of the star stops at a point just below the top of the frame, when in reality it should keep going. This gives away that the star is superimposed over the shot. Oddly enough, when it starts snowing, the effect looks normal.
Revealing mistake: The video image over the building that Al shows Michael Blake is placed incorrectly. The edge of the effect is blatantly visible. This effect is corrected later when Blake asks to see the plaza again and the name is changed.
Revealing mistake: The newspaper Father John holds up has the headline "Youth Hit By Train", but the article text under it talks about Diane Feinstein's election race against John Van de Kamp for California governor in 1990, the year the episode was filmed. Other article texts do not match either. The text under the Bangladesh Flood article talks about Germany's reunification, which also happened in 1990, after the Soviet collapse. The paper is a copy of the Los Angeles Times with the titles and date changed. (00:05:10)
Revealing mistake: Connie and Sam are talking in their room, while Sam is looking at his female self in the mirror. As Connie walks back into the shot, her shadow is cast on the wall behind the mirror. This indicates she came from the opposite direction that is possible in the reflection had this not been the mirror trick. In reality, she would have been coming from behind Sam, not from in front and wouldn't have cast a shadow on the wall with the mirror.
Revealing mistake: Just after Mrs. Stiner delivers the line "My car's out front" after her father's hearing, everyone except Al rushes away from the broken window. Sam brushes up against Al's shirt sleeve, causing it to move. Al, being a hologram, shouldn't have been touched. (00:41:50)